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[v3,3/6] ext4: mark inode dirty before grabbing i_data_sem in ext4_setattr

Message ID 20220419173143.3564144-4-harshads@google.com
State New
Headers show
Series ext4: improve commit path performance for fast commit | expand

Commit Message

harshad shirwadkar April 19, 2022, 5:31 p.m. UTC 
From: Harshad Shirwadkar <harshadshirwadkar@gmail.com>

Mark inode dirty first and then grab i_data_sem in ext4_setattr().

Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
---
 fs/ext4/inode.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

Comments

Jan Kara April 27, 2022, 4:02 p.m. UTC | #1 
On Tue 19-04-22 10:31:40, Harshad Shirwadkar wrote:
> From: Harshad Shirwadkar <harshadshirwadkar@gmail.com>
> 
> Mark inode dirty first and then grab i_data_sem in ext4_setattr().
> 
> Signed-off-by: Harshad Shirwadkar <harshadshirwadkar@gmail.com>

> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index e88940251afd..6eae0804c6fd 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -5455,11 +5455,12 @@ int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
>  					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
>  					inode->i_sb->s_blocksize_bits);
>  
> -			down_write(&EXT4_I(inode)->i_data_sem);
> -			EXT4_I(inode)->i_disksize = attr->ia_size;
>  			rc = ext4_mark_inode_dirty(handle, inode);
>  			if (!error)
>  				error = rc;
> +			down_write(&EXT4_I(inode)->i_data_sem);
> +			EXT4_I(inode)->i_disksize = attr->ia_size;
> +

Hum, this isn't going to fly because ext4_mark_inode_dirty() copies data
from ext4_inode_info to the on-disk buffer and thus new i_disksize will not
be stored on the disk after your change.

								Honza
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Patch

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index e88940251afd..6eae0804c6fd 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5455,11 +5455,12 @@  int ext4_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
 					(attr->ia_size > 0 ? attr->ia_size - 1 : 0) >>
 					inode->i_sb->s_blocksize_bits);
 
-			down_write(&EXT4_I(inode)->i_data_sem);
-			EXT4_I(inode)->i_disksize = attr->ia_size;
 			rc = ext4_mark_inode_dirty(handle, inode);
 			if (!error)
 				error = rc;
+			down_write(&EXT4_I(inode)->i_data_sem);
+			EXT4_I(inode)->i_disksize = attr->ia_size;
+
 			/*
 			 * We have to update i_size under i_data_sem together
 			 * with i_disksize to avoid races with writeback code