[V2,02/13] Consolidate "read callbacks" into a new file

The "read callbacks" code is used by both Ext4 and F2FS. Hence to
remove duplicity, this commit moves the code into
include/linux/read_callbacks.h and fs/read_callbacks.c.

The corresponding decrypt and verity "work" functions have been moved
inside fscrypt and fsverity sources. With these in place, the read
callbacks code now has to just invoke enqueue functions provided by
fscrypt and fsverity.

Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
---
 fs/Kconfig                     |   4 +
 fs/Makefile                    |   4 +
 fs/crypto/Kconfig              |   1 +
 fs/crypto/bio.c                |  23 ++---
 fs/crypto/crypto.c             |  17 +--
 fs/crypto/fscrypt_private.h    |   3 +
 fs/ext4/ext4.h                 |   2 -
 fs/ext4/readpage.c             | 183 +++++----------------------------
 fs/ext4/super.c                |   9 +-
 fs/f2fs/data.c                 | 148 ++++----------------------
 fs/f2fs/super.c                |   9 +-
 fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
 fs/verity/Kconfig              |   1 +
 fs/verity/verify.c             |  12 +++
 include/linux/fscrypt.h        |  20 +---
 include/linux/read_callbacks.h |  21 ++++
 16 files changed, 251 insertions(+), 342 deletions(-)
 create mode 100644 fs/read_callbacks.c
 create mode 100644 include/linux/read_callbacks.h

Hi Chandan,

On Sun, Apr 28, 2019 at 10:01:10AM +0530, Chandan Rajendra wrote:
> The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> remove duplicity, this commit moves the code into
> include/linux/read_callbacks.h and fs/read_callbacks.c.
> 
> The corresponding decrypt and verity "work" functions have been moved
> inside fscrypt and fsverity sources. With these in place, the read
> callbacks code now has to just invoke enqueue functions provided by
> fscrypt and fsverity.
> 
> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> ---
>  fs/Kconfig                     |   4 +
>  fs/Makefile                    |   4 +
>  fs/crypto/Kconfig              |   1 +
>  fs/crypto/bio.c                |  23 ++---
>  fs/crypto/crypto.c             |  17 +--
>  fs/crypto/fscrypt_private.h    |   3 +
>  fs/ext4/ext4.h                 |   2 -
>  fs/ext4/readpage.c             | 183 +++++----------------------------
>  fs/ext4/super.c                |   9 +-
>  fs/f2fs/data.c                 | 148 ++++----------------------
>  fs/f2fs/super.c                |   9 +-
>  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
>  fs/verity/Kconfig              |   1 +
>  fs/verity/verify.c             |  12 +++
>  include/linux/fscrypt.h        |  20 +---
>  include/linux/read_callbacks.h |  21 ++++
>  16 files changed, 251 insertions(+), 342 deletions(-)
>  create mode 100644 fs/read_callbacks.c
>  create mode 100644 include/linux/read_callbacks.h
> 

For easier review, can you split this into multiple patches?  Ideally the ext4
and f2fs patches would be separate, but if that's truly not possible due to
interdependencies it seems you could at least do:

1. Introduce the read_callbacks.
2. Convert encryption to use the read_callbacks.
3. Remove union from struct fscrypt_context.

Also: just FYI, fs-verity isn't upstream yet, and in the past few months I
haven't had much time to work on it.  So you might consider arranging your
series so that initially just fscrypt is supported.  That will be useful on its
own, for block_size < PAGE_SIZE support.  Then fsverity can be added later.

> diff --git a/fs/Kconfig b/fs/Kconfig
> index 97f9eb8df713..03084f2dbeaf 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -308,6 +308,10 @@ config NFS_COMMON
>  	depends on NFSD || NFS_FS || LOCKD
>  	default y
>  
> +config FS_READ_CALLBACKS
> +       bool
> +       default n

'default n' is unnecesary, since 'n' is already the default.

> +
>  source "net/sunrpc/Kconfig"
>  source "fs/ceph/Kconfig"
>  source "fs/cifs/Kconfig"
> diff --git a/fs/Makefile b/fs/Makefile
> index 9dd2186e74b5..e0c0fce8cf40 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -21,6 +21,10 @@ else
>  obj-y +=	no-block.o
>  endif
>  
> +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> +obj-y +=	read_callbacks.o
> +endif
> +

This can be simplified to:

obj-$(CONFIG_FS_READ_CALLBACKS) += read_callbacks.o

> diff --git a/fs/read_callbacks.c b/fs/read_callbacks.c
> new file mode 100644
> index 000000000000..b6d5b95e67d7
> --- /dev/null
> +++ b/fs/read_callbacks.c
> @@ -0,0 +1,136 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file tracks the state machine that needs to be executed after reading
> + * data from files that are encrypted and/or have verity metadata associated
> + * with them.
> + */
> +#include <linux/module.h>
> +#include <linux/mm.h>
> +#include <linux/pagemap.h>
> +#include <linux/bio.h>
> +#include <linux/fscrypt.h>
> +#include <linux/fsverity.h>
> +#include <linux/read_callbacks.h>
> +
> +#define NUM_PREALLOC_POST_READ_CTXS	128
> +
> +static struct kmem_cache *read_callbacks_ctx_cache;
> +static mempool_t *read_callbacks_ctx_pool;
> +
> +/* Read callback state machine steps */
> +enum read_callbacks_step {
> +	STEP_INITIAL = 0,
> +	STEP_DECRYPT,
> +	STEP_VERITY,
> +};
> +
> +void end_read_callbacks(struct bio *bio)
> +{
> +	struct page *page;
> +	struct bio_vec *bv;
> +	int i;
> +	struct bvec_iter_all iter_all;
> +
> +	bio_for_each_segment_all(bv, bio, i, iter_all) {
> +		page = bv->bv_page;
> +
> +		BUG_ON(bio->bi_status);
> +
> +		if (!PageError(page))
> +			SetPageUptodate(page);
> +
> +		unlock_page(page);
> +	}
> +	if (bio->bi_private)
> +		put_read_callbacks_ctx(bio->bi_private);
> +	bio_put(bio);
> +}
> +EXPORT_SYMBOL(end_read_callbacks);

end_read_callbacks() is only called by read_callbacks() just below, so it should
be 'static'.

> +
> +struct read_callbacks_ctx *get_read_callbacks_ctx(struct inode *inode,
> +						struct bio *bio,
> +						pgoff_t index)
> +{
> +	unsigned int read_callbacks_steps = 0;

Rename 'read_callbacks_steps' => 'enabled_steps', since it's clear from context.

> +	struct read_callbacks_ctx *ctx = NULL;
> +
> +	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> +		read_callbacks_steps |= 1 << STEP_DECRYPT;
> +#ifdef CONFIG_FS_VERITY
> +	if (inode->i_verity_info != NULL &&
> +		(index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> +		read_callbacks_steps |= 1 << STEP_VERITY;
> +#endif

To avoid the #ifdef, this should probably be made a function in fsverity.h.

> +	if (read_callbacks_steps) {
> +		ctx = mempool_alloc(read_callbacks_ctx_pool, GFP_NOFS);
> +		if (!ctx)
> +			return ERR_PTR(-ENOMEM);
> +		ctx->bio = bio;
> +		ctx->inode = inode;
> +		ctx->enabled_steps = read_callbacks_steps;
> +		ctx->cur_step = STEP_INITIAL;
> +		bio->bi_private = ctx;
> +	}
> +	return ctx;
> +}
> +EXPORT_SYMBOL(get_read_callbacks_ctx);

The callers don't actually use the returned read_callbacks_ctx.  Instead, they
rely on this function storing it in ->bi_private.  So, this function should just
return an error code, and it should be renamed.  Perhaps:

	int read_callbacks_setup_bio(struct inode *inode, struct bio *bio,
				     pgoff_t first_pgoff);

Please rename 'index' to 'first_pgoff' to make it clearer what it is, given that
a bio can contain many pages.

Please add kerneldoc for this function.

- Eric

On 2019/4/28 12:31, Chandan Rajendra wrote:
> The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> remove duplicity, this commit moves the code into
> include/linux/read_callbacks.h and fs/read_callbacks.c.
> 
> The corresponding decrypt and verity "work" functions have been moved
> inside fscrypt and fsverity sources. With these in place, the read
> callbacks code now has to just invoke enqueue functions provided by
> fscrypt and fsverity.
> 
> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> ---
>  fs/Kconfig                     |   4 +
>  fs/Makefile                    |   4 +
>  fs/crypto/Kconfig              |   1 +
>  fs/crypto/bio.c                |  23 ++---
>  fs/crypto/crypto.c             |  17 +--
>  fs/crypto/fscrypt_private.h    |   3 +
>  fs/ext4/ext4.h                 |   2 -
>  fs/ext4/readpage.c             | 183 +++++----------------------------
>  fs/ext4/super.c                |   9 +-
>  fs/f2fs/data.c                 | 148 ++++----------------------
>  fs/f2fs/super.c                |   9 +-
>  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
>  fs/verity/Kconfig              |   1 +
>  fs/verity/verify.c             |  12 +++
>  include/linux/fscrypt.h        |  20 +---
>  include/linux/read_callbacks.h |  21 ++++
>  16 files changed, 251 insertions(+), 342 deletions(-)
>  create mode 100644 fs/read_callbacks.c
>  create mode 100644 include/linux/read_callbacks.h
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 97f9eb8df713..03084f2dbeaf 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -308,6 +308,10 @@ config NFS_COMMON
>  	depends on NFSD || NFS_FS || LOCKD
>  	default y
>  
> +config FS_READ_CALLBACKS
> +       bool
> +       default n
> +
>  source "net/sunrpc/Kconfig"
>  source "fs/ceph/Kconfig"
>  source "fs/cifs/Kconfig"
> diff --git a/fs/Makefile b/fs/Makefile
> index 9dd2186e74b5..e0c0fce8cf40 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -21,6 +21,10 @@ else
>  obj-y +=	no-block.o
>  endif
>  
> +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> +obj-y +=	read_callbacks.o
> +endif
> +
>  obj-$(CONFIG_PROC_FS) += proc_namespace.o
>  
>  obj-y				+= notify/
> diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> index f0de238000c0..163c328bcbd4 100644
> --- a/fs/crypto/Kconfig
> +++ b/fs/crypto/Kconfig
> @@ -8,6 +8,7 @@ config FS_ENCRYPTION
>  	select CRYPTO_CTS
>  	select CRYPTO_SHA256
>  	select KEYS
> +	select FS_READ_CALLBACKS
>  	help
>  	  Enable encryption of files and directories.  This
>  	  feature is similar to ecryptfs, but it is more memory
> diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
> index 5759bcd018cd..27f5618174f2 100644
> --- a/fs/crypto/bio.c
> +++ b/fs/crypto/bio.c
> @@ -24,6 +24,8 @@
>  #include <linux/module.h>
>  #include <linux/bio.h>
>  #include <linux/namei.h>
> +#include <linux/read_callbacks.h>
> +
>  #include "fscrypt_private.h"
>  
>  static void __fscrypt_decrypt_bio(struct bio *bio, bool done)
> @@ -54,24 +56,15 @@ void fscrypt_decrypt_bio(struct bio *bio)
>  }
>  EXPORT_SYMBOL(fscrypt_decrypt_bio);
>  
> -static void completion_pages(struct work_struct *work)
> +void fscrypt_decrypt_work(struct work_struct *work)
>  {
> -	struct fscrypt_ctx *ctx =
> -		container_of(work, struct fscrypt_ctx, r.work);
> -	struct bio *bio = ctx->r.bio;
> +	struct read_callbacks_ctx *ctx =
> +		container_of(work, struct read_callbacks_ctx, work);
>  
> -	__fscrypt_decrypt_bio(bio, true);
> -	fscrypt_release_ctx(ctx);
> -	bio_put(bio);
> -}
> +	fscrypt_decrypt_bio(ctx->bio);
>  
> -void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, struct bio *bio)
> -{
> -	INIT_WORK(&ctx->r.work, completion_pages);
> -	ctx->r.bio = bio;
> -	fscrypt_enqueue_decrypt_work(&ctx->r.work);
> +	read_callbacks(ctx);
>  }
> -EXPORT_SYMBOL(fscrypt_enqueue_decrypt_bio);
>  
>  void fscrypt_pullback_bio_page(struct page **page, bool restore)
>  {
> @@ -87,7 +80,7 @@ void fscrypt_pullback_bio_page(struct page **page, bool restore)
>  	ctx = (struct fscrypt_ctx *)page_private(bounce_page);
>  
>  	/* restore control page */
> -	*page = ctx->w.control_page;
> +	*page = ctx->control_page;
>  
>  	if (restore)
>  		fscrypt_restore_control_page(bounce_page);
> diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
> index 3fc84bf2b1e5..ffa9302a7351 100644
> --- a/fs/crypto/crypto.c
> +++ b/fs/crypto/crypto.c
> @@ -53,6 +53,7 @@ struct kmem_cache *fscrypt_info_cachep;
>  
>  void fscrypt_enqueue_decrypt_work(struct work_struct *work)
>  {
> +	INIT_WORK(work, fscrypt_decrypt_work);
>  	queue_work(fscrypt_read_workqueue, work);
>  }
>  EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
> @@ -70,11 +71,11 @@ void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
>  {
>  	unsigned long flags;
>  
> -	if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
> -		mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
> -		ctx->w.bounce_page = NULL;
> +	if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->bounce_page) {
> +		mempool_free(ctx->bounce_page, fscrypt_bounce_page_pool);
> +		ctx->bounce_page = NULL;
>  	}
> -	ctx->w.control_page = NULL;
> +	ctx->control_page = NULL;
>  	if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
>  		kmem_cache_free(fscrypt_ctx_cachep, ctx);
>  	} else {
> @@ -194,11 +195,11 @@ int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
>  struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
>  				       gfp_t gfp_flags)
>  {
> -	ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
> -	if (ctx->w.bounce_page == NULL)
> +	ctx->bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
> +	if (ctx->bounce_page == NULL)
>  		return ERR_PTR(-ENOMEM);
>  	ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
> -	return ctx->w.bounce_page;
> +	return ctx->bounce_page;
>  }
>  
>  /**
> @@ -267,7 +268,7 @@ struct page *fscrypt_encrypt_page(const struct inode *inode,
>  	if (IS_ERR(ciphertext_page))
>  		goto errout;
>  
> -	ctx->w.control_page = page;
> +	ctx->control_page = page;
>  	err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
>  				     page, ciphertext_page, len, offs,
>  				     gfp_flags);
> diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
> index 7da276159593..412a3bcf9efd 100644
> --- a/fs/crypto/fscrypt_private.h
> +++ b/fs/crypto/fscrypt_private.h
> @@ -114,6 +114,9 @@ static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
>  	return false;
>  }
>  
> +/* bio.c */
> +void fscrypt_decrypt_work(struct work_struct *work);
> +
>  /* crypto.c */
>  extern struct kmem_cache *fscrypt_info_cachep;
>  extern int fscrypt_initialize(unsigned int cop_flags);
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index f2b0e628ff7b..23f8568c9b53 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -3127,8 +3127,6 @@ static inline void ext4_set_de_type(struct super_block *sb,
>  extern int ext4_mpage_readpages(struct address_space *mapping,
>  				struct list_head *pages, struct page *page,
>  				unsigned nr_pages, bool is_readahead);
> -extern int __init ext4_init_post_read_processing(void);
> -extern void ext4_exit_post_read_processing(void);
>  
>  /* symlink.c */
>  extern const struct inode_operations ext4_encrypted_symlink_inode_operations;
> diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> index 0169e3809da3..e363dededc21 100644
> --- a/fs/ext4/readpage.c
> +++ b/fs/ext4/readpage.c
> @@ -44,14 +44,10 @@
>  #include <linux/backing-dev.h>
>  #include <linux/pagevec.h>
>  #include <linux/cleancache.h>
> +#include <linux/read_callbacks.h>
>  
>  #include "ext4.h"
>  
> -#define NUM_PREALLOC_POST_READ_CTXS	128
> -
> -static struct kmem_cache *bio_post_read_ctx_cache;
> -static mempool_t *bio_post_read_ctx_pool;
> -
>  static inline bool ext4_bio_encrypted(struct bio *bio)
>  {
>  #ifdef CONFIG_FS_ENCRYPTION
> @@ -61,125 +57,6 @@ static inline bool ext4_bio_encrypted(struct bio *bio)
>  #endif
>  }
>  
> -/* postprocessing steps for read bios */
> -enum bio_post_read_step {
> -	STEP_INITIAL = 0,
> -	STEP_DECRYPT,
> -	STEP_VERITY,
> -};
> -
> -struct bio_post_read_ctx {
> -	struct bio *bio;
> -	struct work_struct work;
> -	unsigned int cur_step;
> -	unsigned int enabled_steps;
> -};
> -
> -static void __read_end_io(struct bio *bio)
> -{
> -	struct page *page;
> -	struct bio_vec *bv;
> -	int i;
> -	struct bvec_iter_all iter_all;
> -
> -	bio_for_each_segment_all(bv, bio, i, iter_all) {
> -		page = bv->bv_page;
> -
> -		/* PG_error was set if any post_read step failed */
> -		if (bio->bi_status || PageError(page)) {
> -			ClearPageUptodate(page);
> -			SetPageError(page);
> -		} else {
> -			SetPageUptodate(page);
> -		}
> -		unlock_page(page);
> -	}
> -	if (bio->bi_private)
> -		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
> -	bio_put(bio);
> -}
> -
> -static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> -
> -static void decrypt_work(struct work_struct *work)
> -{
> -	struct bio_post_read_ctx *ctx =
> -		container_of(work, struct bio_post_read_ctx, work);
> -
> -	fscrypt_decrypt_bio(ctx->bio);
> -
> -	bio_post_read_processing(ctx);
> -}
> -
> -static void verity_work(struct work_struct *work)
> -{
> -	struct bio_post_read_ctx *ctx =
> -		container_of(work, struct bio_post_read_ctx, work);
> -
> -	fsverity_verify_bio(ctx->bio);
> -
> -	bio_post_read_processing(ctx);
> -}
> -
> -static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> -{
> -	/*
> -	 * We use different work queues for decryption and for verity because
> -	 * verity may require reading metadata pages that need decryption, and
> -	 * we shouldn't recurse to the same workqueue.
> -	 */
> -	switch (++ctx->cur_step) {
> -	case STEP_DECRYPT:
> -		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> -			INIT_WORK(&ctx->work, decrypt_work);
> -			fscrypt_enqueue_decrypt_work(&ctx->work);
> -			return;
> -		}
> -		ctx->cur_step++;
> -		/* fall-through */
> -	case STEP_VERITY:
> -		if (ctx->enabled_steps & (1 << STEP_VERITY)) {
> -			INIT_WORK(&ctx->work, verity_work);
> -			fsverity_enqueue_verify_work(&ctx->work);
> -			return;
> -		}
> -		ctx->cur_step++;
> -		/* fall-through */
> -	default:
> -		__read_end_io(ctx->bio);
> -	}
> -}
> -
> -static struct bio_post_read_ctx *get_bio_post_read_ctx(struct inode *inode,
> -						       struct bio *bio,
> -						       pgoff_t index)
> -{
> -	unsigned int post_read_steps = 0;
> -	struct bio_post_read_ctx *ctx = NULL;
> -
> -	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> -		post_read_steps |= 1 << STEP_DECRYPT;
> -#ifdef CONFIG_FS_VERITY
> -	if (inode->i_verity_info != NULL &&
> -	    (index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> -		post_read_steps |= 1 << STEP_VERITY;
> -#endif
> -	if (post_read_steps) {
> -		ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
> -		if (!ctx)
> -			return ERR_PTR(-ENOMEM);
> -		ctx->bio = bio;
> -		ctx->enabled_steps = post_read_steps;
> -		bio->bi_private = ctx;
> -	}
> -	return ctx;
> -}
> -
> -static bool bio_post_read_required(struct bio *bio)
> -{
> -	return bio->bi_private && !bio->bi_status;
> -}
> -
>  /*
>   * I/O completion handler for multipage BIOs.
>   *
> @@ -194,14 +71,30 @@ static bool bio_post_read_required(struct bio *bio)
>   */
>  static void mpage_end_io(struct bio *bio)
>  {
> -	if (bio_post_read_required(bio)) {
> -		struct bio_post_read_ctx *ctx = bio->bi_private;
> +	struct bio_vec *bv;
> +	int i;
> +	struct bvec_iter_all iter_all;
> +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> +	if (read_callbacks_required(bio)) {
> +		struct read_callbacks_ctx *ctx = bio->bi_private;
>  
> -		ctx->cur_step = STEP_INITIAL;
> -		bio_post_read_processing(ctx);
> +		read_callbacks(ctx);
>  		return;
>  	}
> -	__read_end_io(bio);
> +#endif
> +	bio_for_each_segment_all(bv, bio, i, iter_all) {
> +		struct page *page = bv->bv_page;
> +
> +		if (!bio->bi_status) {
> +			SetPageUptodate(page);
> +		} else {
> +			ClearPageUptodate(page);
> +			SetPageError(page);
> +		}
> +		unlock_page(page);
> +	}
> +
> +	bio_put(bio);
>  }
>  
>  static inline loff_t ext4_readpage_limit(struct inode *inode)
> @@ -368,17 +261,19 @@ int ext4_mpage_readpages(struct address_space *mapping,
>  			bio = NULL;
>  		}
>  		if (bio == NULL) {
> -			struct bio_post_read_ctx *ctx;
> +			struct read_callbacks_ctx *ctx = NULL;
>  
>  			bio = bio_alloc(GFP_KERNEL,
>  				min_t(int, nr_pages, BIO_MAX_PAGES));
>  			if (!bio)
>  				goto set_error_page;
> -			ctx = get_bio_post_read_ctx(inode, bio, page->index);
> +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> +			ctx = get_read_callbacks_ctx(inode, bio, page->index);
>  			if (IS_ERR(ctx)) {
>  				bio_put(bio);
>  				goto set_error_page;
>  			}
> +#endif
>  			bio_set_dev(bio, bdev);
>  			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
>  			bio->bi_end_io = mpage_end_io;
> @@ -417,29 +312,3 @@ int ext4_mpage_readpages(struct address_space *mapping,
>  		submit_bio(bio);
>  	return 0;
>  }
> -
> -int __init ext4_init_post_read_processing(void)
> -{
> -	bio_post_read_ctx_cache =
> -		kmem_cache_create("ext4_bio_post_read_ctx",
> -				  sizeof(struct bio_post_read_ctx), 0, 0, NULL);
> -	if (!bio_post_read_ctx_cache)
> -		goto fail;
> -	bio_post_read_ctx_pool =
> -		mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
> -					 bio_post_read_ctx_cache);
> -	if (!bio_post_read_ctx_pool)
> -		goto fail_free_cache;
> -	return 0;
> -
> -fail_free_cache:
> -	kmem_cache_destroy(bio_post_read_ctx_cache);
> -fail:
> -	return -ENOMEM;
> -}
> -
> -void ext4_exit_post_read_processing(void)
> -{
> -	mempool_destroy(bio_post_read_ctx_pool);
> -	kmem_cache_destroy(bio_post_read_ctx_cache);
> -}
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 4ae6f5849caa..aba724f82cc3 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -6101,10 +6101,6 @@ static int __init ext4_init_fs(void)
>  		return err;
>  
>  	err = ext4_init_pending();
> -	if (err)
> -		goto out7;
> -
> -	err = ext4_init_post_read_processing();
>  	if (err)
>  		goto out6;
>  
> @@ -6146,10 +6142,8 @@ static int __init ext4_init_fs(void)
>  out4:
>  	ext4_exit_pageio();
>  out5:
> -	ext4_exit_post_read_processing();
> -out6:
>  	ext4_exit_pending();
> -out7:
> +out6:
>  	ext4_exit_es();
>  
>  	return err;
> @@ -6166,7 +6160,6 @@ static void __exit ext4_exit_fs(void)
>  	ext4_exit_sysfs();
>  	ext4_exit_system_zone();
>  	ext4_exit_pageio();
> -	ext4_exit_post_read_processing();
>  	ext4_exit_es();
>  	ext4_exit_pending();
>  }
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 038b958d0fa9..05430d3650ab 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -18,6 +18,7 @@
>  #include <linux/uio.h>
>  #include <linux/cleancache.h>
>  #include <linux/sched/signal.h>
> +#include <linux/read_callbacks.h>
>  
>  #include "f2fs.h"
>  #include "node.h"
> @@ -25,11 +26,6 @@
>  #include "trace.h"
>  #include <trace/events/f2fs.h>
>  
> -#define NUM_PREALLOC_POST_READ_CTXS	128
> -
> -static struct kmem_cache *bio_post_read_ctx_cache;
> -static mempool_t *bio_post_read_ctx_pool;
> -
>  static bool __is_cp_guaranteed(struct page *page)
>  {
>  	struct address_space *mapping = page->mapping;
> @@ -69,20 +65,6 @@ static enum count_type __read_io_type(struct page *page)
>  	return F2FS_RD_DATA;
>  }
>  
> -/* postprocessing steps for read bios */
> -enum bio_post_read_step {
> -	STEP_INITIAL = 0,
> -	STEP_DECRYPT,
> -	STEP_VERITY,
> -};
> -
> -struct bio_post_read_ctx {
> -	struct bio *bio;
> -	struct work_struct work;
> -	unsigned int cur_step;
> -	unsigned int enabled_steps;
> -};
> -
>  static void __read_end_io(struct bio *bio)
>  {
>  	struct page *page;
> @@ -104,65 +86,16 @@ static void __read_end_io(struct bio *bio)
>  		dec_page_count(F2FS_P_SB(page), __read_io_type(page));
>  		unlock_page(page);
>  	}
> -	if (bio->bi_private)
> -		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
> -	bio_put(bio);
> -}
> -
> -static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
>  
> -static void decrypt_work(struct work_struct *work)
> -{
> -	struct bio_post_read_ctx *ctx =
> -		container_of(work, struct bio_post_read_ctx, work);
> -
> -	fscrypt_decrypt_bio(ctx->bio);
> +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> +	if (bio->bi_private) {
> +		struct read_callbacks_ctx *ctx;
>  
> -	bio_post_read_processing(ctx);
> -}
> -
> -static void verity_work(struct work_struct *work)
> -{
> -	struct bio_post_read_ctx *ctx =
> -		container_of(work, struct bio_post_read_ctx, work);
> -
> -	fsverity_verify_bio(ctx->bio);
> -
> -	bio_post_read_processing(ctx);
> -}
> -
> -static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> -{
> -	/*
> -	 * We use different work queues for decryption and for verity because
> -	 * verity may require reading metadata pages that need decryption, and
> -	 * we shouldn't recurse to the same workqueue.
> -	 */
> -	switch (++ctx->cur_step) {
> -	case STEP_DECRYPT:
> -		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> -			INIT_WORK(&ctx->work, decrypt_work);
> -			fscrypt_enqueue_decrypt_work(&ctx->work);
> -			return;
> -		}
> -		ctx->cur_step++;
> -		/* fall-through */
> -	case STEP_VERITY:
> -		if (ctx->enabled_steps & (1 << STEP_VERITY)) {
> -			INIT_WORK(&ctx->work, verity_work);
> -			fsverity_enqueue_verify_work(&ctx->work);
> -			return;
> -		}
> -		ctx->cur_step++;
> -		/* fall-through */
> -	default:
> -		__read_end_io(ctx->bio);
> +		ctx = bio->bi_private;
> +		put_read_callbacks_ctx(ctx);
>  	}
> -}
> -
> -static bool f2fs_bio_post_read_required(struct bio *bio)
> -{
> -	return bio->bi_private && !bio->bi_status;
> +#endif
> +	bio_put(bio);
>  }
>  
>  static void f2fs_read_end_io(struct bio *bio)
> @@ -173,14 +106,12 @@ static void f2fs_read_end_io(struct bio *bio)
>  		bio->bi_status = BLK_STS_IOERR;
>  	}
>  
> -	if (f2fs_bio_post_read_required(bio)) {
> -		struct bio_post_read_ctx *ctx = bio->bi_private;
> -
> -		ctx->cur_step = STEP_INITIAL;
> -		bio_post_read_processing(ctx);
> +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> +	if (!bio->bi_status && bio->bi_private) {
> +		read_callbacks((struct read_callbacks_ctx *)(bio->bi_private));
>  		return;

Previously, in __read_end_io() we will decrease in-flight read IO count for each
page, but it looks in the case that if fscrypto or fsverity is on and there is
no IO error in end_io(), we will miss handling the count.

> @@ -104,65 +86,16 @@ static void __read_end_io(struct bio *bio)
>  		dec_page_count(F2FS_P_SB(page), __read_io_type(page));

Thanks,

>  	}
> -
> +#endif
>  	__read_end_io(bio);
>  }
>  
> @@ -582,9 +513,9 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>  {
>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>  	struct bio *bio;
> -	struct bio_post_read_ctx *ctx;
> -	unsigned int post_read_steps = 0;
> -
> +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> +	struct read_callbacks_ctx *ctx;
> +#endif
>  	if (!f2fs_is_valid_blkaddr(sbi, blkaddr, DATA_GENERIC))
>  		return ERR_PTR(-EFAULT);
>  
> @@ -595,24 +526,13 @@ static struct bio *f2fs_grab_read_bio(struct inode *inode, block_t blkaddr,
>  	bio->bi_end_io = f2fs_read_end_io;
>  	bio_set_op_attrs(bio, REQ_OP_READ, op_flag);
>  
> -	if (f2fs_encrypted_file(inode))
> -		post_read_steps |= 1 << STEP_DECRYPT;
> -#ifdef CONFIG_FS_VERITY
> -	if (inode->i_verity_info != NULL &&
> -	    (first_idx < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> -		post_read_steps |= 1 << STEP_VERITY;
> -#endif
> -	if (post_read_steps) {
> -		ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
> -		if (!ctx) {
> -			bio_put(bio);
> -			return ERR_PTR(-ENOMEM);
> -		}
> -		ctx->bio = bio;
> -		ctx->enabled_steps = post_read_steps;
> -		bio->bi_private = ctx;
> +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> +	ctx = get_read_callbacks_ctx(inode, bio, first_idx);
> +	if (IS_ERR(ctx)) {
> +		bio_put(bio);
> +		return (struct bio *)ctx;
>  	}
> -
> +#endif
>  	return bio;
>  }
>  
> @@ -2894,29 +2814,3 @@ void f2fs_clear_page_cache_dirty_tag(struct page *page)
>  						PAGECACHE_TAG_DIRTY);
>  	xa_unlock_irqrestore(&mapping->i_pages, flags);
>  }
> -
> -int __init f2fs_init_post_read_processing(void)
> -{
> -	bio_post_read_ctx_cache =
> -		kmem_cache_create("f2fs_bio_post_read_ctx",
> -				  sizeof(struct bio_post_read_ctx), 0, 0, NULL);
> -	if (!bio_post_read_ctx_cache)
> -		goto fail;
> -	bio_post_read_ctx_pool =
> -		mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
> -					 bio_post_read_ctx_cache);
> -	if (!bio_post_read_ctx_pool)
> -		goto fail_free_cache;
> -	return 0;
> -
> -fail_free_cache:
> -	kmem_cache_destroy(bio_post_read_ctx_cache);
> -fail:
> -	return -ENOMEM;
> -}
> -
> -void __exit f2fs_destroy_post_read_processing(void)
> -{
> -	mempool_destroy(bio_post_read_ctx_pool);
> -	kmem_cache_destroy(bio_post_read_ctx_cache);
> -}
> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> index 0e187f67b206..2f75f06c784a 100644
> --- a/fs/f2fs/super.c
> +++ b/fs/f2fs/super.c
> @@ -3633,15 +3633,11 @@ static int __init init_f2fs_fs(void)
>  	err = register_filesystem(&f2fs_fs_type);
>  	if (err)
>  		goto free_shrinker;
> +
>  	f2fs_create_root_stats();
> -	err = f2fs_init_post_read_processing();
> -	if (err)
> -		goto free_root_stats;
> +
>  	return 0;
>  
> -free_root_stats:
> -	f2fs_destroy_root_stats();
> -	unregister_filesystem(&f2fs_fs_type);
>  free_shrinker:
>  	unregister_shrinker(&f2fs_shrinker_info);
>  free_sysfs:
> @@ -3662,7 +3658,6 @@ static int __init init_f2fs_fs(void)
>  
>  static void __exit exit_f2fs_fs(void)
>  {
> -	f2fs_destroy_post_read_processing();
>  	f2fs_destroy_root_stats();
>  	unregister_filesystem(&f2fs_fs_type);
>  	unregister_shrinker(&f2fs_shrinker_info);
> diff --git a/fs/read_callbacks.c b/fs/read_callbacks.c
> new file mode 100644
> index 000000000000..b6d5b95e67d7
> --- /dev/null
> +++ b/fs/read_callbacks.c
> @@ -0,0 +1,136 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * This file tracks the state machine that needs to be executed after reading
> + * data from files that are encrypted and/or have verity metadata associated
> + * with them.
> + */
> +#include <linux/module.h>
> +#include <linux/mm.h>
> +#include <linux/pagemap.h>
> +#include <linux/bio.h>
> +#include <linux/fscrypt.h>
> +#include <linux/fsverity.h>
> +#include <linux/read_callbacks.h>
> +
> +#define NUM_PREALLOC_POST_READ_CTXS	128
> +
> +static struct kmem_cache *read_callbacks_ctx_cache;
> +static mempool_t *read_callbacks_ctx_pool;
> +
> +/* Read callback state machine steps */
> +enum read_callbacks_step {
> +	STEP_INITIAL = 0,
> +	STEP_DECRYPT,
> +	STEP_VERITY,
> +};
> +
> +void end_read_callbacks(struct bio *bio)
> +{
> +	struct page *page;
> +	struct bio_vec *bv;
> +	int i;
> +	struct bvec_iter_all iter_all;
> +
> +	bio_for_each_segment_all(bv, bio, i, iter_all) {
> +		page = bv->bv_page;
> +
> +		BUG_ON(bio->bi_status);
> +
> +		if (!PageError(page))
> +			SetPageUptodate(page);
> +
> +		unlock_page(page);
> +	}
> +	if (bio->bi_private)
> +		put_read_callbacks_ctx(bio->bi_private);
> +	bio_put(bio);
> +}
> +EXPORT_SYMBOL(end_read_callbacks);
> +
> +void read_callbacks(struct read_callbacks_ctx *ctx)
> +{
> +	/*
> +	 * We use different work queues for decryption and for verity because
> +	 * verity may require reading metadata pages that need decryption, and
> +	 * we shouldn't recurse to the same workqueue.
> +	 */
> +	switch (++ctx->cur_step) {
> +	case STEP_DECRYPT:
> +		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> +			fscrypt_enqueue_decrypt_work(&ctx->work);
> +			return;
> +		}
> +		ctx->cur_step++;
> +		/* fall-through */
> +	case STEP_VERITY:
> +		if (ctx->enabled_steps & (1 << STEP_VERITY)) {
> +			fsverity_enqueue_verify_work(&ctx->work);
> +			return;
> +		}
> +		ctx->cur_step++;
> +		/* fall-through */
> +	default:
> +		end_read_callbacks(ctx->bio);
> +	}
> +}
> +EXPORT_SYMBOL(read_callbacks);
> +
> +struct read_callbacks_ctx *get_read_callbacks_ctx(struct inode *inode,
> +						struct bio *bio,
> +						pgoff_t index)
> +{
> +	unsigned int read_callbacks_steps = 0;
> +	struct read_callbacks_ctx *ctx = NULL;
> +
> +	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> +		read_callbacks_steps |= 1 << STEP_DECRYPT;
> +#ifdef CONFIG_FS_VERITY
> +	if (inode->i_verity_info != NULL &&
> +		(index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> +		read_callbacks_steps |= 1 << STEP_VERITY;
> +#endif
> +	if (read_callbacks_steps) {
> +		ctx = mempool_alloc(read_callbacks_ctx_pool, GFP_NOFS);
> +		if (!ctx)
> +			return ERR_PTR(-ENOMEM);
> +		ctx->bio = bio;
> +		ctx->inode = inode;
> +		ctx->enabled_steps = read_callbacks_steps;
> +		ctx->cur_step = STEP_INITIAL;
> +		bio->bi_private = ctx;
> +	}
> +	return ctx;
> +}
> +EXPORT_SYMBOL(get_read_callbacks_ctx);
> +
> +void put_read_callbacks_ctx(struct read_callbacks_ctx *ctx)
> +{
> +	mempool_free(ctx, read_callbacks_ctx_pool);
> +}
> +EXPORT_SYMBOL(put_read_callbacks_ctx);
> +
> +bool read_callbacks_required(struct bio *bio)
> +{
> +	return bio->bi_private && !bio->bi_status;
> +}
> +EXPORT_SYMBOL(read_callbacks_required);
> +
> +static int __init init_read_callbacks(void)
> +{
> +	read_callbacks_ctx_cache = KMEM_CACHE(read_callbacks_ctx, 0);
> +	if (!read_callbacks_ctx_cache)
> +		goto fail;
> +	read_callbacks_ctx_pool =
> +		mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
> +					 read_callbacks_ctx_cache);
> +	if (!read_callbacks_ctx_pool)
> +		goto fail_free_cache;
> +	return 0;
> +
> +fail_free_cache:
> +	kmem_cache_destroy(read_callbacks_ctx_cache);
> +fail:
> +	return -ENOMEM;
> +}
> +
> +fs_initcall(init_read_callbacks);
> diff --git a/fs/verity/Kconfig b/fs/verity/Kconfig
> index 563593fb42db..44784e57c99d 100644
> --- a/fs/verity/Kconfig
> +++ b/fs/verity/Kconfig
> @@ -4,6 +4,7 @@ config FS_VERITY
>  	# SHA-256 is selected as it's intended to be the default hash algorithm.
>  	# To avoid bloat, other wanted algorithms must be selected explicitly.
>  	select CRYPTO_SHA256
> +	select FS_READ_CALLBACKS
>  	help
>  	  This option enables fs-verity.  fs-verity is the dm-verity
>  	  mechanism implemented at the file level.  On supported
> diff --git a/fs/verity/verify.c b/fs/verity/verify.c
> index 5732453a81e7..f93bee33872d 100644
> --- a/fs/verity/verify.c
> +++ b/fs/verity/verify.c
> @@ -13,6 +13,7 @@
>  #include <linux/pagemap.h>
>  #include <linux/ratelimit.h>
>  #include <linux/scatterlist.h>
> +#include <linux/read_callbacks.h>
>  
>  struct workqueue_struct *fsverity_read_workqueue;
>  
> @@ -284,6 +285,16 @@ void fsverity_verify_bio(struct bio *bio)
>  EXPORT_SYMBOL_GPL(fsverity_verify_bio);
>  #endif /* CONFIG_BLOCK */
>  
> +static void fsverity_verify_work(struct work_struct *work)
> +{
> +	struct read_callbacks_ctx *ctx =
> +		container_of(work, struct read_callbacks_ctx, work);
> +
> +	fsverity_verify_bio(ctx->bio);
> +
> +	read_callbacks(ctx);
> +}
> +
>  /**
>   * fsverity_enqueue_verify_work - enqueue work on the fs-verity workqueue
>   *
> @@ -291,6 +302,7 @@ EXPORT_SYMBOL_GPL(fsverity_verify_bio);
>   */
>  void fsverity_enqueue_verify_work(struct work_struct *work)
>  {
> +	INIT_WORK(work, fsverity_verify_work);
>  	queue_work(fsverity_read_workqueue, work);
>  }
>  EXPORT_SYMBOL_GPL(fsverity_enqueue_verify_work);
> diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
> index c00b764d6b8c..a760b7bd81d4 100644
> --- a/include/linux/fscrypt.h
> +++ b/include/linux/fscrypt.h
> @@ -68,11 +68,7 @@ struct fscrypt_ctx {
>  		struct {
>  			struct page *bounce_page;	/* Ciphertext page */
>  			struct page *control_page;	/* Original page  */
> -		} w;
> -		struct {
> -			struct bio *bio;
> -			struct work_struct work;
> -		} r;
> +		};
>  		struct list_head free_list;	/* Free list */
>  	};
>  	u8 flags;				/* Flags */
> @@ -113,7 +109,7 @@ extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned in
>  
>  static inline struct page *fscrypt_control_page(struct page *page)
>  {
> -	return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
> +	return ((struct fscrypt_ctx *)page_private(page))->control_page;
>  }
>  
>  extern void fscrypt_restore_control_page(struct page *);
> @@ -218,9 +214,6 @@ static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
>  }
>  
>  /* bio.c */
> -extern void fscrypt_decrypt_bio(struct bio *);
> -extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
> -					struct bio *bio);
>  extern void fscrypt_pullback_bio_page(struct page **, bool);
>  extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
>  				 unsigned int);
> @@ -390,15 +383,6 @@ static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
>  	return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
>  }
>  
> -/* bio.c */
> -static inline void fscrypt_decrypt_bio(struct bio *bio)
> -{
> -}
> -
> -static inline void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
> -					       struct bio *bio)
> -{
> -}
>  
>  static inline void fscrypt_pullback_bio_page(struct page **page, bool restore)
>  {
> diff --git a/include/linux/read_callbacks.h b/include/linux/read_callbacks.h
> new file mode 100644
> index 000000000000..c501cdf83a5b
> --- /dev/null
> +++ b/include/linux/read_callbacks.h
> @@ -0,0 +1,21 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _READ_CALLBACKS_H
> +#define _READ_CALLBACKS_H
> +
> +struct read_callbacks_ctx {
> +	struct bio *bio;
> +	struct inode *inode;
> +	struct work_struct work;
> +	unsigned int cur_step;
> +	unsigned int enabled_steps;
> +};
> +
> +void end_read_callbacks(struct bio *bio);
> +void read_callbacks(struct read_callbacks_ctx *ctx);
> +struct read_callbacks_ctx *get_read_callbacks_ctx(struct inode *inode,
> +						struct bio *bio,
> +						pgoff_t index);
> +void put_read_callbacks_ctx(struct read_callbacks_ctx *ctx);
> +bool read_callbacks_required(struct bio *bio);
> +
> +#endif	/* _READ_CALLBACKS_H */
>

On Sun, Apr 28, 2019 at 10:01:10AM +0530, Chandan Rajendra wrote:
> The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> remove duplicity, this commit moves the code into
> include/linux/read_callbacks.h and fs/read_callbacks.c.
> 
> The corresponding decrypt and verity "work" functions have been moved
> inside fscrypt and fsverity sources. With these in place, the read
> callbacks code now has to just invoke enqueue functions provided by
> fscrypt and fsverity.
> 
> Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> ---
>  fs/Kconfig                     |   4 +
>  fs/Makefile                    |   4 +
>  fs/crypto/Kconfig              |   1 +
>  fs/crypto/bio.c                |  23 ++---
>  fs/crypto/crypto.c             |  17 +--
>  fs/crypto/fscrypt_private.h    |   3 +
>  fs/ext4/ext4.h                 |   2 -
>  fs/ext4/readpage.c             | 183 +++++----------------------------
>  fs/ext4/super.c                |   9 +-
>  fs/f2fs/data.c                 | 148 ++++----------------------
>  fs/f2fs/super.c                |   9 +-
>  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
>  fs/verity/Kconfig              |   1 +
>  fs/verity/verify.c             |  12 +++
>  include/linux/fscrypt.h        |  20 +---
>  include/linux/read_callbacks.h |  21 ++++
>  16 files changed, 251 insertions(+), 342 deletions(-)
>  create mode 100644 fs/read_callbacks.c
>  create mode 100644 include/linux/read_callbacks.h
> 
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 97f9eb8df713..03084f2dbeaf 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -308,6 +308,10 @@ config NFS_COMMON
>  	depends on NFSD || NFS_FS || LOCKD
>  	default y
>  
> +config FS_READ_CALLBACKS
> +       bool
> +       default n
> +
>  source "net/sunrpc/Kconfig"
>  source "fs/ceph/Kconfig"
>  source "fs/cifs/Kconfig"

This shouldn't be under the 'if NETWORK_FILESYSTEMS' block, since it has nothing
to do with network filesystems.  When trying to compile this I got:

	WARNING: unmet direct dependencies detected for FS_READ_CALLBACKS
	  Depends on [n]: NETWORK_FILESYSTEMS [=n]
	  Selected by [y]:
	  - FS_ENCRYPTION [=y]
	  - FS_VERITY [=y]

Perhaps put it just below FS_IOMAP?

> diff --git a/fs/Makefile b/fs/Makefile
> index 9dd2186e74b5..e0c0fce8cf40 100644
> --- a/fs/Makefile
> +++ b/fs/Makefile
> @@ -21,6 +21,10 @@ else
>  obj-y +=	no-block.o
>  endif
>  
> +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> +obj-y +=	read_callbacks.o
> +endif
> +
>  obj-$(CONFIG_PROC_FS) += proc_namespace.o
>  
>  obj-y				+= notify/
> diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> index f0de238000c0..163c328bcbd4 100644
> --- a/fs/crypto/Kconfig
> +++ b/fs/crypto/Kconfig
> @@ -8,6 +8,7 @@ config FS_ENCRYPTION
>  	select CRYPTO_CTS
>  	select CRYPTO_SHA256
>  	select KEYS
> +	select FS_READ_CALLBACKS
>  	help
>  	  Enable encryption of files and directories.  This
>  	  feature is similar to ecryptfs, but it is more memory

This selection needs to be conditional on BLOCK.

	select FS_READ_CALLBACKS if BLOCK

Otherwise, building without BLOCK and with UBIFS encryption support fails.

	fs/read_callbacks.c: In function ‘end_read_callbacks’:
	fs/read_callbacks.c:34:23: error: storage size of ‘iter_all’ isn’t known
	  struct bvec_iter_all iter_all;
			       ^~~~~~~~
	fs/read_callbacks.c:37:20: error: dereferencing pointer to incomplete type ‘struct buffer_head’
	   if (!PageError(bh->b_page))

	[...]

- Eric

On Tuesday, April 30, 2019 5:30:28 AM IST Eric Biggers wrote:
> Hi Chandan,
> 
> On Sun, Apr 28, 2019 at 10:01:10AM +0530, Chandan Rajendra wrote:
> > The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> > remove duplicity, this commit moves the code into
> > include/linux/read_callbacks.h and fs/read_callbacks.c.
> > 
> > The corresponding decrypt and verity "work" functions have been moved
> > inside fscrypt and fsverity sources. With these in place, the read
> > callbacks code now has to just invoke enqueue functions provided by
> > fscrypt and fsverity.
> > 
> > Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> > ---
> >  fs/Kconfig                     |   4 +
> >  fs/Makefile                    |   4 +
> >  fs/crypto/Kconfig              |   1 +
> >  fs/crypto/bio.c                |  23 ++---
> >  fs/crypto/crypto.c             |  17 +--
> >  fs/crypto/fscrypt_private.h    |   3 +
> >  fs/ext4/ext4.h                 |   2 -
> >  fs/ext4/readpage.c             | 183 +++++----------------------------
> >  fs/ext4/super.c                |   9 +-
> >  fs/f2fs/data.c                 | 148 ++++----------------------
> >  fs/f2fs/super.c                |   9 +-
> >  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
> >  fs/verity/Kconfig              |   1 +
> >  fs/verity/verify.c             |  12 +++
> >  include/linux/fscrypt.h        |  20 +---
> >  include/linux/read_callbacks.h |  21 ++++
> >  16 files changed, 251 insertions(+), 342 deletions(-)
> >  create mode 100644 fs/read_callbacks.c
> >  create mode 100644 include/linux/read_callbacks.h
> > 
> 
> For easier review, can you split this into multiple patches?  Ideally the ext4
> and f2fs patches would be separate, but if that's truly not possible due to
> interdependencies it seems you could at least do:
> 
> 1. Introduce the read_callbacks.
> 2. Convert encryption to use the read_callbacks.
> 3. Remove union from struct fscrypt_context.
> 
> Also: just FYI, fs-verity isn't upstream yet, and in the past few months I
> haven't had much time to work on it.  So you might consider arranging your
> series so that initially just fscrypt is supported.  That will be useful on its
> own, for block_size < PAGE_SIZE support.  Then fsverity can be added later.
> 
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 97f9eb8df713..03084f2dbeaf 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -308,6 +308,10 @@ config NFS_COMMON
> >  	depends on NFSD || NFS_FS || LOCKD
> >  	default y
> >  
> > +config FS_READ_CALLBACKS
> > +       bool
> > +       default n
> 
> 'default n' is unnecesary, since 'n' is already the default.
> 
> > +
> >  source "net/sunrpc/Kconfig"
> >  source "fs/ceph/Kconfig"
> >  source "fs/cifs/Kconfig"
> > diff --git a/fs/Makefile b/fs/Makefile
> > index 9dd2186e74b5..e0c0fce8cf40 100644
> > --- a/fs/Makefile
> > +++ b/fs/Makefile
> > @@ -21,6 +21,10 @@ else
> >  obj-y +=	no-block.o
> >  endif
> >  
> > +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> > +obj-y +=	read_callbacks.o
> > +endif
> > +
> 
> This can be simplified to:
> 
> obj-$(CONFIG_FS_READ_CALLBACKS) += read_callbacks.o
> 
> > diff --git a/fs/read_callbacks.c b/fs/read_callbacks.c
> > new file mode 100644
> > index 000000000000..b6d5b95e67d7
> > --- /dev/null
> > +++ b/fs/read_callbacks.c
> > @@ -0,0 +1,136 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * This file tracks the state machine that needs to be executed after reading
> > + * data from files that are encrypted and/or have verity metadata associated
> > + * with them.
> > + */
> > +#include <linux/module.h>
> > +#include <linux/mm.h>
> > +#include <linux/pagemap.h>
> > +#include <linux/bio.h>
> > +#include <linux/fscrypt.h>
> > +#include <linux/fsverity.h>
> > +#include <linux/read_callbacks.h>
> > +
> > +#define NUM_PREALLOC_POST_READ_CTXS	128
> > +
> > +static struct kmem_cache *read_callbacks_ctx_cache;
> > +static mempool_t *read_callbacks_ctx_pool;
> > +
> > +/* Read callback state machine steps */
> > +enum read_callbacks_step {
> > +	STEP_INITIAL = 0,
> > +	STEP_DECRYPT,
> > +	STEP_VERITY,
> > +};
> > +
> > +void end_read_callbacks(struct bio *bio)
> > +{
> > +	struct page *page;
> > +	struct bio_vec *bv;
> > +	int i;
> > +	struct bvec_iter_all iter_all;
> > +
> > +	bio_for_each_segment_all(bv, bio, i, iter_all) {
> > +		page = bv->bv_page;
> > +
> > +		BUG_ON(bio->bi_status);
> > +
> > +		if (!PageError(page))
> > +			SetPageUptodate(page);
> > +
> > +		unlock_page(page);
> > +	}
> > +	if (bio->bi_private)
> > +		put_read_callbacks_ctx(bio->bi_private);
> > +	bio_put(bio);
> > +}
> > +EXPORT_SYMBOL(end_read_callbacks);
> 
> end_read_callbacks() is only called by read_callbacks() just below, so it should
> be 'static'.
> 
> > +
> > +struct read_callbacks_ctx *get_read_callbacks_ctx(struct inode *inode,
> > +						struct bio *bio,
> > +						pgoff_t index)
> > +{
> > +	unsigned int read_callbacks_steps = 0;
> 
> Rename 'read_callbacks_steps' => 'enabled_steps', since it's clear from context.
> 
> > +	struct read_callbacks_ctx *ctx = NULL;
> > +
> > +	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> > +		read_callbacks_steps |= 1 << STEP_DECRYPT;
> > +#ifdef CONFIG_FS_VERITY
> > +	if (inode->i_verity_info != NULL &&
> > +		(index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> > +		read_callbacks_steps |= 1 << STEP_VERITY;
> > +#endif
> 
> To avoid the #ifdef, this should probably be made a function in fsverity.h.
> 
> > +	if (read_callbacks_steps) {
> > +		ctx = mempool_alloc(read_callbacks_ctx_pool, GFP_NOFS);
> > +		if (!ctx)
> > +			return ERR_PTR(-ENOMEM);
> > +		ctx->bio = bio;
> > +		ctx->inode = inode;
> > +		ctx->enabled_steps = read_callbacks_steps;
> > +		ctx->cur_step = STEP_INITIAL;
> > +		bio->bi_private = ctx;
> > +	}
> > +	return ctx;
> > +}
> > +EXPORT_SYMBOL(get_read_callbacks_ctx);
> 
> The callers don't actually use the returned read_callbacks_ctx.  Instead, they
> rely on this function storing it in ->bi_private.  So, this function should just
> return an error code, and it should be renamed.  Perhaps:
> 
> 	int read_callbacks_setup_bio(struct inode *inode, struct bio *bio,
> 				     pgoff_t first_pgoff);
> 
> Please rename 'index' to 'first_pgoff' to make it clearer what it is, given that
> a bio can contain many pages.
> 
> Please add kerneldoc for this function.
> 

I will implement the changes suggested above.

On Tuesday, April 30, 2019 7:07:28 AM IST Chao Yu wrote:
> On 2019/4/28 12:31, Chandan Rajendra wrote:
> > The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> > remove duplicity, this commit moves the code into
> > include/linux/read_callbacks.h and fs/read_callbacks.c.
> > 
> > The corresponding decrypt and verity "work" functions have been moved
> > inside fscrypt and fsverity sources. With these in place, the read
> > callbacks code now has to just invoke enqueue functions provided by
> > fscrypt and fsverity.
> > 
> > Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> > ---
> >  fs/Kconfig                     |   4 +
> >  fs/Makefile                    |   4 +
> >  fs/crypto/Kconfig              |   1 +
> >  fs/crypto/bio.c                |  23 ++---
> >  fs/crypto/crypto.c             |  17 +--
> >  fs/crypto/fscrypt_private.h    |   3 +
> >  fs/ext4/ext4.h                 |   2 -
> >  fs/ext4/readpage.c             | 183 +++++----------------------------
> >  fs/ext4/super.c                |   9 +-
> >  fs/f2fs/data.c                 | 148 ++++----------------------
> >  fs/f2fs/super.c                |   9 +-
> >  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
> >  fs/verity/Kconfig              |   1 +
> >  fs/verity/verify.c             |  12 +++
> >  include/linux/fscrypt.h        |  20 +---
> >  include/linux/read_callbacks.h |  21 ++++
> >  16 files changed, 251 insertions(+), 342 deletions(-)
> >  create mode 100644 fs/read_callbacks.c
> >  create mode 100644 include/linux/read_callbacks.h
> > 
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 97f9eb8df713..03084f2dbeaf 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -308,6 +308,10 @@ config NFS_COMMON
> >  	depends on NFSD || NFS_FS || LOCKD
> >  	default y
> >  
> > +config FS_READ_CALLBACKS
> > +       bool
> > +       default n
> > +
> >  source "net/sunrpc/Kconfig"
> >  source "fs/ceph/Kconfig"
> >  source "fs/cifs/Kconfig"
> > diff --git a/fs/Makefile b/fs/Makefile
> > index 9dd2186e74b5..e0c0fce8cf40 100644
> > --- a/fs/Makefile
> > +++ b/fs/Makefile
> > @@ -21,6 +21,10 @@ else
> >  obj-y +=	no-block.o
> >  endif
> >  
> > +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> > +obj-y +=	read_callbacks.o
> > +endif
> > +
> >  obj-$(CONFIG_PROC_FS) += proc_namespace.o
> >  
> >  obj-y				+= notify/
> > diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> > index f0de238000c0..163c328bcbd4 100644
> > --- a/fs/crypto/Kconfig
> > +++ b/fs/crypto/Kconfig
> > @@ -8,6 +8,7 @@ config FS_ENCRYPTION
> >  	select CRYPTO_CTS
> >  	select CRYPTO_SHA256
> >  	select KEYS
> > +	select FS_READ_CALLBACKS
> >  	help
> >  	  Enable encryption of files and directories.  This
> >  	  feature is similar to ecryptfs, but it is more memory
> > diff --git a/fs/crypto/bio.c b/fs/crypto/bio.c
> > index 5759bcd018cd..27f5618174f2 100644
> > --- a/fs/crypto/bio.c
> > +++ b/fs/crypto/bio.c
> > @@ -24,6 +24,8 @@
> >  #include <linux/module.h>
> >  #include <linux/bio.h>
> >  #include <linux/namei.h>
> > +#include <linux/read_callbacks.h>
> > +
> >  #include "fscrypt_private.h"
> >  
> >  static void __fscrypt_decrypt_bio(struct bio *bio, bool done)
> > @@ -54,24 +56,15 @@ void fscrypt_decrypt_bio(struct bio *bio)
> >  }
> >  EXPORT_SYMBOL(fscrypt_decrypt_bio);
> >  
> > -static void completion_pages(struct work_struct *work)
> > +void fscrypt_decrypt_work(struct work_struct *work)
> >  {
> > -	struct fscrypt_ctx *ctx =
> > -		container_of(work, struct fscrypt_ctx, r.work);
> > -	struct bio *bio = ctx->r.bio;
> > +	struct read_callbacks_ctx *ctx =
> > +		container_of(work, struct read_callbacks_ctx, work);
> >  
> > -	__fscrypt_decrypt_bio(bio, true);
> > -	fscrypt_release_ctx(ctx);
> > -	bio_put(bio);
> > -}
> > +	fscrypt_decrypt_bio(ctx->bio);
> >  
> > -void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx, struct bio *bio)
> > -{
> > -	INIT_WORK(&ctx->r.work, completion_pages);
> > -	ctx->r.bio = bio;
> > -	fscrypt_enqueue_decrypt_work(&ctx->r.work);
> > +	read_callbacks(ctx);
> >  }
> > -EXPORT_SYMBOL(fscrypt_enqueue_decrypt_bio);
> >  
> >  void fscrypt_pullback_bio_page(struct page **page, bool restore)
> >  {
> > @@ -87,7 +80,7 @@ void fscrypt_pullback_bio_page(struct page **page, bool restore)
> >  	ctx = (struct fscrypt_ctx *)page_private(bounce_page);
> >  
> >  	/* restore control page */
> > -	*page = ctx->w.control_page;
> > +	*page = ctx->control_page;
> >  
> >  	if (restore)
> >  		fscrypt_restore_control_page(bounce_page);
> > diff --git a/fs/crypto/crypto.c b/fs/crypto/crypto.c
> > index 3fc84bf2b1e5..ffa9302a7351 100644
> > --- a/fs/crypto/crypto.c
> > +++ b/fs/crypto/crypto.c
> > @@ -53,6 +53,7 @@ struct kmem_cache *fscrypt_info_cachep;
> >  
> >  void fscrypt_enqueue_decrypt_work(struct work_struct *work)
> >  {
> > +	INIT_WORK(work, fscrypt_decrypt_work);
> >  	queue_work(fscrypt_read_workqueue, work);
> >  }
> >  EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
> > @@ -70,11 +71,11 @@ void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
> >  {
> >  	unsigned long flags;
> >  
> > -	if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
> > -		mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
> > -		ctx->w.bounce_page = NULL;
> > +	if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->bounce_page) {
> > +		mempool_free(ctx->bounce_page, fscrypt_bounce_page_pool);
> > +		ctx->bounce_page = NULL;
> >  	}
> > -	ctx->w.control_page = NULL;
> > +	ctx->control_page = NULL;
> >  	if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
> >  		kmem_cache_free(fscrypt_ctx_cachep, ctx);
> >  	} else {
> > @@ -194,11 +195,11 @@ int fscrypt_do_page_crypto(const struct inode *inode, fscrypt_direction_t rw,
> >  struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
> >  				       gfp_t gfp_flags)
> >  {
> > -	ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
> > -	if (ctx->w.bounce_page == NULL)
> > +	ctx->bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
> > +	if (ctx->bounce_page == NULL)
> >  		return ERR_PTR(-ENOMEM);
> >  	ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
> > -	return ctx->w.bounce_page;
> > +	return ctx->bounce_page;
> >  }
> >  
> >  /**
> > @@ -267,7 +268,7 @@ struct page *fscrypt_encrypt_page(const struct inode *inode,
> >  	if (IS_ERR(ciphertext_page))
> >  		goto errout;
> >  
> > -	ctx->w.control_page = page;
> > +	ctx->control_page = page;
> >  	err = fscrypt_do_page_crypto(inode, FS_ENCRYPT, lblk_num,
> >  				     page, ciphertext_page, len, offs,
> >  				     gfp_flags);
> > diff --git a/fs/crypto/fscrypt_private.h b/fs/crypto/fscrypt_private.h
> > index 7da276159593..412a3bcf9efd 100644
> > --- a/fs/crypto/fscrypt_private.h
> > +++ b/fs/crypto/fscrypt_private.h
> > @@ -114,6 +114,9 @@ static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
> >  	return false;
> >  }
> >  
> > +/* bio.c */
> > +void fscrypt_decrypt_work(struct work_struct *work);
> > +
> >  /* crypto.c */
> >  extern struct kmem_cache *fscrypt_info_cachep;
> >  extern int fscrypt_initialize(unsigned int cop_flags);
> > diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> > index f2b0e628ff7b..23f8568c9b53 100644
> > --- a/fs/ext4/ext4.h
> > +++ b/fs/ext4/ext4.h
> > @@ -3127,8 +3127,6 @@ static inline void ext4_set_de_type(struct super_block *sb,
> >  extern int ext4_mpage_readpages(struct address_space *mapping,
> >  				struct list_head *pages, struct page *page,
> >  				unsigned nr_pages, bool is_readahead);
> > -extern int __init ext4_init_post_read_processing(void);
> > -extern void ext4_exit_post_read_processing(void);
> >  
> >  /* symlink.c */
> >  extern const struct inode_operations ext4_encrypted_symlink_inode_operations;
> > diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
> > index 0169e3809da3..e363dededc21 100644
> > --- a/fs/ext4/readpage.c
> > +++ b/fs/ext4/readpage.c
> > @@ -44,14 +44,10 @@
> >  #include <linux/backing-dev.h>
> >  #include <linux/pagevec.h>
> >  #include <linux/cleancache.h>
> > +#include <linux/read_callbacks.h>
> >  
> >  #include "ext4.h"
> >  
> > -#define NUM_PREALLOC_POST_READ_CTXS	128
> > -
> > -static struct kmem_cache *bio_post_read_ctx_cache;
> > -static mempool_t *bio_post_read_ctx_pool;
> > -
> >  static inline bool ext4_bio_encrypted(struct bio *bio)
> >  {
> >  #ifdef CONFIG_FS_ENCRYPTION
> > @@ -61,125 +57,6 @@ static inline bool ext4_bio_encrypted(struct bio *bio)
> >  #endif
> >  }
> >  
> > -/* postprocessing steps for read bios */
> > -enum bio_post_read_step {
> > -	STEP_INITIAL = 0,
> > -	STEP_DECRYPT,
> > -	STEP_VERITY,
> > -};
> > -
> > -struct bio_post_read_ctx {
> > -	struct bio *bio;
> > -	struct work_struct work;
> > -	unsigned int cur_step;
> > -	unsigned int enabled_steps;
> > -};
> > -
> > -static void __read_end_io(struct bio *bio)
> > -{
> > -	struct page *page;
> > -	struct bio_vec *bv;
> > -	int i;
> > -	struct bvec_iter_all iter_all;
> > -
> > -	bio_for_each_segment_all(bv, bio, i, iter_all) {
> > -		page = bv->bv_page;
> > -
> > -		/* PG_error was set if any post_read step failed */
> > -		if (bio->bi_status || PageError(page)) {
> > -			ClearPageUptodate(page);
> > -			SetPageError(page);
> > -		} else {
> > -			SetPageUptodate(page);
> > -		}
> > -		unlock_page(page);
> > -	}
> > -	if (bio->bi_private)
> > -		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
> > -	bio_put(bio);
> > -}
> > -
> > -static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> > -
> > -static void decrypt_work(struct work_struct *work)
> > -{
> > -	struct bio_post_read_ctx *ctx =
> > -		container_of(work, struct bio_post_read_ctx, work);
> > -
> > -	fscrypt_decrypt_bio(ctx->bio);
> > -
> > -	bio_post_read_processing(ctx);
> > -}
> > -
> > -static void verity_work(struct work_struct *work)
> > -{
> > -	struct bio_post_read_ctx *ctx =
> > -		container_of(work, struct bio_post_read_ctx, work);
> > -
> > -	fsverity_verify_bio(ctx->bio);
> > -
> > -	bio_post_read_processing(ctx);
> > -}
> > -
> > -static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> > -{
> > -	/*
> > -	 * We use different work queues for decryption and for verity because
> > -	 * verity may require reading metadata pages that need decryption, and
> > -	 * we shouldn't recurse to the same workqueue.
> > -	 */
> > -	switch (++ctx->cur_step) {
> > -	case STEP_DECRYPT:
> > -		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> > -			INIT_WORK(&ctx->work, decrypt_work);
> > -			fscrypt_enqueue_decrypt_work(&ctx->work);
> > -			return;
> > -		}
> > -		ctx->cur_step++;
> > -		/* fall-through */
> > -	case STEP_VERITY:
> > -		if (ctx->enabled_steps & (1 << STEP_VERITY)) {
> > -			INIT_WORK(&ctx->work, verity_work);
> > -			fsverity_enqueue_verify_work(&ctx->work);
> > -			return;
> > -		}
> > -		ctx->cur_step++;
> > -		/* fall-through */
> > -	default:
> > -		__read_end_io(ctx->bio);
> > -	}
> > -}
> > -
> > -static struct bio_post_read_ctx *get_bio_post_read_ctx(struct inode *inode,
> > -						       struct bio *bio,
> > -						       pgoff_t index)
> > -{
> > -	unsigned int post_read_steps = 0;
> > -	struct bio_post_read_ctx *ctx = NULL;
> > -
> > -	if (IS_ENCRYPTED(inode) && S_ISREG(inode->i_mode))
> > -		post_read_steps |= 1 << STEP_DECRYPT;
> > -#ifdef CONFIG_FS_VERITY
> > -	if (inode->i_verity_info != NULL &&
> > -	    (index < ((i_size_read(inode) + PAGE_SIZE - 1) >> PAGE_SHIFT)))
> > -		post_read_steps |= 1 << STEP_VERITY;
> > -#endif
> > -	if (post_read_steps) {
> > -		ctx = mempool_alloc(bio_post_read_ctx_pool, GFP_NOFS);
> > -		if (!ctx)
> > -			return ERR_PTR(-ENOMEM);
> > -		ctx->bio = bio;
> > -		ctx->enabled_steps = post_read_steps;
> > -		bio->bi_private = ctx;
> > -	}
> > -	return ctx;
> > -}
> > -
> > -static bool bio_post_read_required(struct bio *bio)
> > -{
> > -	return bio->bi_private && !bio->bi_status;
> > -}
> > -
> >  /*
> >   * I/O completion handler for multipage BIOs.
> >   *
> > @@ -194,14 +71,30 @@ static bool bio_post_read_required(struct bio *bio)
> >   */
> >  static void mpage_end_io(struct bio *bio)
> >  {
> > -	if (bio_post_read_required(bio)) {
> > -		struct bio_post_read_ctx *ctx = bio->bi_private;
> > +	struct bio_vec *bv;
> > +	int i;
> > +	struct bvec_iter_all iter_all;
> > +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> > +	if (read_callbacks_required(bio)) {
> > +		struct read_callbacks_ctx *ctx = bio->bi_private;
> >  
> > -		ctx->cur_step = STEP_INITIAL;
> > -		bio_post_read_processing(ctx);
> > +		read_callbacks(ctx);
> >  		return;
> >  	}
> > -	__read_end_io(bio);
> > +#endif
> > +	bio_for_each_segment_all(bv, bio, i, iter_all) {
> > +		struct page *page = bv->bv_page;
> > +
> > +		if (!bio->bi_status) {
> > +			SetPageUptodate(page);
> > +		} else {
> > +			ClearPageUptodate(page);
> > +			SetPageError(page);
> > +		}
> > +		unlock_page(page);
> > +	}
> > +
> > +	bio_put(bio);
> >  }
> >  
> >  static inline loff_t ext4_readpage_limit(struct inode *inode)
> > @@ -368,17 +261,19 @@ int ext4_mpage_readpages(struct address_space *mapping,
> >  			bio = NULL;
> >  		}
> >  		if (bio == NULL) {
> > -			struct bio_post_read_ctx *ctx;
> > +			struct read_callbacks_ctx *ctx = NULL;
> >  
> >  			bio = bio_alloc(GFP_KERNEL,
> >  				min_t(int, nr_pages, BIO_MAX_PAGES));
> >  			if (!bio)
> >  				goto set_error_page;
> > -			ctx = get_bio_post_read_ctx(inode, bio, page->index);
> > +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> > +			ctx = get_read_callbacks_ctx(inode, bio, page->index);
> >  			if (IS_ERR(ctx)) {
> >  				bio_put(bio);
> >  				goto set_error_page;
> >  			}
> > +#endif
> >  			bio_set_dev(bio, bdev);
> >  			bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
> >  			bio->bi_end_io = mpage_end_io;
> > @@ -417,29 +312,3 @@ int ext4_mpage_readpages(struct address_space *mapping,
> >  		submit_bio(bio);
> >  	return 0;
> >  }
> > -
> > -int __init ext4_init_post_read_processing(void)
> > -{
> > -	bio_post_read_ctx_cache =
> > -		kmem_cache_create("ext4_bio_post_read_ctx",
> > -				  sizeof(struct bio_post_read_ctx), 0, 0, NULL);
> > -	if (!bio_post_read_ctx_cache)
> > -		goto fail;
> > -	bio_post_read_ctx_pool =
> > -		mempool_create_slab_pool(NUM_PREALLOC_POST_READ_CTXS,
> > -					 bio_post_read_ctx_cache);
> > -	if (!bio_post_read_ctx_pool)
> > -		goto fail_free_cache;
> > -	return 0;
> > -
> > -fail_free_cache:
> > -	kmem_cache_destroy(bio_post_read_ctx_cache);
> > -fail:
> > -	return -ENOMEM;
> > -}
> > -
> > -void ext4_exit_post_read_processing(void)
> > -{
> > -	mempool_destroy(bio_post_read_ctx_pool);
> > -	kmem_cache_destroy(bio_post_read_ctx_cache);
> > -}
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index 4ae6f5849caa..aba724f82cc3 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -6101,10 +6101,6 @@ static int __init ext4_init_fs(void)
> >  		return err;
> >  
> >  	err = ext4_init_pending();
> > -	if (err)
> > -		goto out7;
> > -
> > -	err = ext4_init_post_read_processing();
> >  	if (err)
> >  		goto out6;
> >  
> > @@ -6146,10 +6142,8 @@ static int __init ext4_init_fs(void)
> >  out4:
> >  	ext4_exit_pageio();
> >  out5:
> > -	ext4_exit_post_read_processing();
> > -out6:
> >  	ext4_exit_pending();
> > -out7:
> > +out6:
> >  	ext4_exit_es();
> >  
> >  	return err;
> > @@ -6166,7 +6160,6 @@ static void __exit ext4_exit_fs(void)
> >  	ext4_exit_sysfs();
> >  	ext4_exit_system_zone();
> >  	ext4_exit_pageio();
> > -	ext4_exit_post_read_processing();
> >  	ext4_exit_es();
> >  	ext4_exit_pending();
> >  }
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 038b958d0fa9..05430d3650ab 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/uio.h>
> >  #include <linux/cleancache.h>
> >  #include <linux/sched/signal.h>
> > +#include <linux/read_callbacks.h>
> >  
> >  #include "f2fs.h"
> >  #include "node.h"
> > @@ -25,11 +26,6 @@
> >  #include "trace.h"
> >  #include <trace/events/f2fs.h>
> >  
> > -#define NUM_PREALLOC_POST_READ_CTXS	128
> > -
> > -static struct kmem_cache *bio_post_read_ctx_cache;
> > -static mempool_t *bio_post_read_ctx_pool;
> > -
> >  static bool __is_cp_guaranteed(struct page *page)
> >  {
> >  	struct address_space *mapping = page->mapping;
> > @@ -69,20 +65,6 @@ static enum count_type __read_io_type(struct page *page)
> >  	return F2FS_RD_DATA;
> >  }
> >  
> > -/* postprocessing steps for read bios */
> > -enum bio_post_read_step {
> > -	STEP_INITIAL = 0,
> > -	STEP_DECRYPT,
> > -	STEP_VERITY,
> > -};
> > -
> > -struct bio_post_read_ctx {
> > -	struct bio *bio;
> > -	struct work_struct work;
> > -	unsigned int cur_step;
> > -	unsigned int enabled_steps;
> > -};
> > -
> >  static void __read_end_io(struct bio *bio)
> >  {
> >  	struct page *page;
> > @@ -104,65 +86,16 @@ static void __read_end_io(struct bio *bio)
> >  		dec_page_count(F2FS_P_SB(page), __read_io_type(page));
> >  		unlock_page(page);
> >  	}
> > -	if (bio->bi_private)
> > -		mempool_free(bio->bi_private, bio_post_read_ctx_pool);
> > -	bio_put(bio);
> > -}
> > -
> > -static void bio_post_read_processing(struct bio_post_read_ctx *ctx);
> >  
> > -static void decrypt_work(struct work_struct *work)
> > -{
> > -	struct bio_post_read_ctx *ctx =
> > -		container_of(work, struct bio_post_read_ctx, work);
> > -
> > -	fscrypt_decrypt_bio(ctx->bio);
> > +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> > +	if (bio->bi_private) {
> > +		struct read_callbacks_ctx *ctx;
> >  
> > -	bio_post_read_processing(ctx);
> > -}
> > -
> > -static void verity_work(struct work_struct *work)
> > -{
> > -	struct bio_post_read_ctx *ctx =
> > -		container_of(work, struct bio_post_read_ctx, work);
> > -
> > -	fsverity_verify_bio(ctx->bio);
> > -
> > -	bio_post_read_processing(ctx);
> > -}
> > -
> > -static void bio_post_read_processing(struct bio_post_read_ctx *ctx)
> > -{
> > -	/*
> > -	 * We use different work queues for decryption and for verity because
> > -	 * verity may require reading metadata pages that need decryption, and
> > -	 * we shouldn't recurse to the same workqueue.
> > -	 */
> > -	switch (++ctx->cur_step) {
> > -	case STEP_DECRYPT:
> > -		if (ctx->enabled_steps & (1 << STEP_DECRYPT)) {
> > -			INIT_WORK(&ctx->work, decrypt_work);
> > -			fscrypt_enqueue_decrypt_work(&ctx->work);
> > -			return;
> > -		}
> > -		ctx->cur_step++;
> > -		/* fall-through */
> > -	case STEP_VERITY:
> > -		if (ctx->enabled_steps & (1 << STEP_VERITY)) {
> > -			INIT_WORK(&ctx->work, verity_work);
> > -			fsverity_enqueue_verify_work(&ctx->work);
> > -			return;
> > -		}
> > -		ctx->cur_step++;
> > -		/* fall-through */
> > -	default:
> > -		__read_end_io(ctx->bio);
> > +		ctx = bio->bi_private;
> > +		put_read_callbacks_ctx(ctx);
> >  	}
> > -}
> > -
> > -static bool f2fs_bio_post_read_required(struct bio *bio)
> > -{
> > -	return bio->bi_private && !bio->bi_status;
> > +#endif
> > +	bio_put(bio);
> >  }
> >  
> >  static void f2fs_read_end_io(struct bio *bio)
> > @@ -173,14 +106,12 @@ static void f2fs_read_end_io(struct bio *bio)
> >  		bio->bi_status = BLK_STS_IOERR;
> >  	}
> >  
> > -	if (f2fs_bio_post_read_required(bio)) {
> > -		struct bio_post_read_ctx *ctx = bio->bi_private;
> > -
> > -		ctx->cur_step = STEP_INITIAL;
> > -		bio_post_read_processing(ctx);
> > +#if defined(CONFIG_FS_ENCRYPTION) || defined(CONFIG_FS_VERITY)
> > +	if (!bio->bi_status && bio->bi_private) {
> > +		read_callbacks((struct read_callbacks_ctx *)(bio->bi_private));
> >  		return;
> 
> Previously, in __read_end_io() we will decrease in-flight read IO count for each
> page, but it looks in the case that if fscrypto or fsverity is on and there is
> no IO error in end_io(), we will miss handling the count.
> 

Thanks for pointing this out. I will fix this in the next version of this
patchset.

On Tuesday, April 30, 2019 11:35:08 PM IST Eric Biggers wrote:
> On Sun, Apr 28, 2019 at 10:01:10AM +0530, Chandan Rajendra wrote:
> > The "read callbacks" code is used by both Ext4 and F2FS. Hence to
> > remove duplicity, this commit moves the code into
> > include/linux/read_callbacks.h and fs/read_callbacks.c.
> > 
> > The corresponding decrypt and verity "work" functions have been moved
> > inside fscrypt and fsverity sources. With these in place, the read
> > callbacks code now has to just invoke enqueue functions provided by
> > fscrypt and fsverity.
> > 
> > Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
> > ---
> >  fs/Kconfig                     |   4 +
> >  fs/Makefile                    |   4 +
> >  fs/crypto/Kconfig              |   1 +
> >  fs/crypto/bio.c                |  23 ++---
> >  fs/crypto/crypto.c             |  17 +--
> >  fs/crypto/fscrypt_private.h    |   3 +
> >  fs/ext4/ext4.h                 |   2 -
> >  fs/ext4/readpage.c             | 183 +++++----------------------------
> >  fs/ext4/super.c                |   9 +-
> >  fs/f2fs/data.c                 | 148 ++++----------------------
> >  fs/f2fs/super.c                |   9 +-
> >  fs/read_callbacks.c            | 136 ++++++++++++++++++++++++
> >  fs/verity/Kconfig              |   1 +
> >  fs/verity/verify.c             |  12 +++
> >  include/linux/fscrypt.h        |  20 +---
> >  include/linux/read_callbacks.h |  21 ++++
> >  16 files changed, 251 insertions(+), 342 deletions(-)
> >  create mode 100644 fs/read_callbacks.c
> >  create mode 100644 include/linux/read_callbacks.h
> > 
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index 97f9eb8df713..03084f2dbeaf 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -308,6 +308,10 @@ config NFS_COMMON
> >  	depends on NFSD || NFS_FS || LOCKD
> >  	default y
> >  
> > +config FS_READ_CALLBACKS
> > +       bool
> > +       default n
> > +
> >  source "net/sunrpc/Kconfig"
> >  source "fs/ceph/Kconfig"
> >  source "fs/cifs/Kconfig"
> 
> This shouldn't be under the 'if NETWORK_FILESYSTEMS' block, since it has nothing
> to do with network filesystems.  When trying to compile this I got:
> 
> 	WARNING: unmet direct dependencies detected for FS_READ_CALLBACKS
> 	  Depends on [n]: NETWORK_FILESYSTEMS [=n]
> 	  Selected by [y]:
> 	  - FS_ENCRYPTION [=y]
> 	  - FS_VERITY [=y]
> 
> Perhaps put it just below FS_IOMAP?
> 
> > diff --git a/fs/Makefile b/fs/Makefile
> > index 9dd2186e74b5..e0c0fce8cf40 100644
> > --- a/fs/Makefile
> > +++ b/fs/Makefile
> > @@ -21,6 +21,10 @@ else
> >  obj-y +=	no-block.o
> >  endif
> >  
> > +ifeq ($(CONFIG_FS_READ_CALLBACKS),y)
> > +obj-y +=	read_callbacks.o
> > +endif
> > +
> >  obj-$(CONFIG_PROC_FS) += proc_namespace.o
> >  
> >  obj-y				+= notify/
> > diff --git a/fs/crypto/Kconfig b/fs/crypto/Kconfig
> > index f0de238000c0..163c328bcbd4 100644
> > --- a/fs/crypto/Kconfig
> > +++ b/fs/crypto/Kconfig
> > @@ -8,6 +8,7 @@ config FS_ENCRYPTION
> >  	select CRYPTO_CTS
> >  	select CRYPTO_SHA256
> >  	select KEYS
> > +	select FS_READ_CALLBACKS
> >  	help
> >  	  Enable encryption of files and directories.  This
> >  	  feature is similar to ecryptfs, but it is more memory
> 
> This selection needs to be conditional on BLOCK.
> 
> 	select FS_READ_CALLBACKS if BLOCK
> 
> Otherwise, building without BLOCK and with UBIFS encryption support fails.
> 
> 	fs/read_callbacks.c: In function ‘end_read_callbacks’:
> 	fs/read_callbacks.c:34:23: error: storage size of ‘iter_all’ isn’t known
> 	  struct bvec_iter_all iter_all;
> 			       ^~~~~~~~
> 	fs/read_callbacks.c:37:20: error: dereferencing pointer to incomplete type ‘struct buffer_head’
> 	   if (!PageError(bh->b_page))
> 
> 	[...]
>

I will fix this in the next version of this patchset.