| Message ID | 20100810232321.0eb72247.toshi.okajima@jp.fujitsu.com |
|---|---|
| State | New, archived |
| Headers | show |
On 2010-08-10, at 10:23, Toshiyuki Okajima wrote: > Table. the max file size which we can write or seek > at each filesystem feature tuning and file flag setting > +===============================+===============================+ > | | | > | !EXT4_EXTENTS_FL | EXT4_EXTETNS_FL | > | | | > +-------------------------------+-------------------------------+ > | write: 2194719883264 | write: -------------- | > | seek: 2199023251456 | seek: -------------- | > +-------------------------------+-------------------------------+ > | write: 4402345721856 | write: 17592186044415 | > | seek: 17592186044415 | seek: 17592186044415 | > +-------------------------------+-------------------------------+ Interesting. The 2TB vs. 4TB difference for block-mapped files is due to the removal of the 2^32 sectors limit imposed by i_blocks, and is not strictly related to extents. > +loff_t ext4_llseek(struct file *file, loff_t offset, int origin) > +{ > + struct inode *inode = file->f_mapping->host; > + loff_t maxbytes; > + > + mutex_lock(&inode->i_mutex); > + if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) > + maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes; > + else > + maxbytes = inode->i_sb->s_maxbytes; This part doesn't really have to be under i_mutex. Otherwise, the patch looks reasonable. > + switch (origin) { > + case SEEK_END: > + offset += inode->i_size; > + break; > + case SEEK_CUR: > + if (offset == 0) { > + mutex_unlock(&inode->i_mutex); > + return file->f_pos; > + } > + offset += file->f_pos; > + break; > + } > + > + if (offset < 0 || offset > maxbytes) { > + mutex_unlock(&inode->i_mutex); > + return -EINVAL; > + } > + > + if (offset != file->f_pos) { > + file->f_pos = offset; > + file->f_version = 0; > + } > + mutex_unlock(&inode->i_mutex); > + > + return offset; > +} It's too bad that we have to duplicate the whole generic_file_llseek() code here, but I don't think there is a better solution. However, it is worthwhile to add a comment to this function like: /* copied from generic_file_llseek() to handle both block-mapped and * extent-mapped maxbytes values. Should otherwise be identical. */ Cheers, Andreas -- Andreas Dilger Lustre Technical Lead Oracle Corporation Canada Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi. (2010/08/10 15:35), Andreas Dilger wrote: > > On 2010-08-10, at 10:23, Toshiyuki Okajima wrote: <snip> >> +loff_t ext4_llseek(struct file *file, loff_t offset, int origin) >> +{ >> + struct inode *inode = file->f_mapping->host; >> + loff_t maxbytes; >> + >> + mutex_lock(&inode->i_mutex); >> + if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) >> + maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes; >> + else >> + maxbytes = inode->i_sb->s_maxbytes; > > This part doesn't really have to be under i_mutex. Otherwise, the patch looks reasonable. OK. > >> + switch (origin) { >> + case SEEK_END: >> + offset += inode->i_size; >> + break; >> + case SEEK_CUR: >> + if (offset == 0) { >> + mutex_unlock(&inode->i_mutex); >> + return file->f_pos; >> + } >> + offset += file->f_pos; >> + break; >> + } >> + >> + if (offset< 0 || offset> maxbytes) { >> + mutex_unlock(&inode->i_mutex); >> + return -EINVAL; >> + } >> + >> + if (offset != file->f_pos) { >> + file->f_pos = offset; >> + file->f_version = 0; >> + } >> + mutex_unlock(&inode->i_mutex); >> + >> + return offset; >> +} > > It's too bad that we have to duplicate the whole generic_file_llseek() code here, but I don't think there is a better solution. However, it is worthwhile to add a comment to this function like: > > /* copied from generic_file_llseek() to handle both block-mapped and > * extent-mapped maxbytes values. Should otherwise be identical. */ I understand it. I apply your comments and then rebuild my patch. Immediately I'll send it. Thanks, Toshiyuki Okajima -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
================================================================================
Subject: [PATCH] ext4: create own llseek function to handle the max file size correctly.
From: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
If the file has no EXT4_EXTENTS_FL flag, the maximum size which can be written
(write systemcall) is different from the maximum size which can be seeked
(lseek systemcall).
For example, the following 2 cases show us the differences:
#1: mkfs.ext3 <dev>; mount -t ext4 <dev>
#2: mkfs.ext3 <dev>; tune2fs -Oextent,huge_file <dev>; mount -t ext4 <dev>
Table. the max file size which we can write or seek
at each filesystem feature tuning and file flag setting
+============+===============================+===============================+
| \ File flag| | |
| \ | !EXT4_EXTENTS_FL | EXT4_EXTETNS_FL |
|case \| | |
+------------+-------------------------------+-------------------------------+
| #1 | write: 2194719883264 | write: -------------- |
| | seek: 2199023251456 | seek: -------------- |
+------------+-------------------------------+-------------------------------+
| #2 | write: 4402345721856 | write: 17592186044415 |
| | seek: 17592186044415 | seek: 17592186044415 |
+------------+-------------------------------+-------------------------------+
The differences exist because ext4 has 2 max-file-size (sb->s_maxbytes,
EXT4_SB(sb)->s_bitmap_maxbytes) although generic_file_llseek uses only
sb->s_maxbytes. (llseek of ext4_file_operations is generic_file_llseek.)
Therefore we create own llseek function which uses 2 max-file-size.
The new own function originates from generic_file_llseek_nolocked().
If the file flag, "EXT4_EXTENTS_FL" is not set, the function alters
inode->i_sb->s_maxbytes into EXT4_SB(inode->i_sb)->s_bitmap_maxbytes.
Signed-off-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
---
fs/ext4/dir.c | 2 +-
fs/ext4/ext4.h | 1 +
fs/ext4/file.c | 39 ++++++++++++++++++++++++++++++++++++++-
3 files changed, 40 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
index ea5e6cb..62c9bba 100644
--- a/fs/ext4/dir.c
+++ b/fs/ext4/dir.c
@@ -39,7 +39,7 @@ static int ext4_release_dir(struct inode *inode,
struct file *filp);
const struct file_operations ext4_dir_operations = {
- .llseek = generic_file_llseek,
+ .llseek = ext4_llseek,
.read = generic_read_dir,
.readdir = ext4_readdir, /* we take BKL. needed?*/
.unlocked_ioctl = ext4_ioctl,
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 19a4de5..e7050cd 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1870,6 +1870,7 @@ extern const struct file_operations ext4_dir_operations;
/* file.c */
extern const struct inode_operations ext4_file_inode_operations;
extern const struct file_operations ext4_file_operations;
+extern loff_t ext4_llseek(struct file *file, loff_t offset, int origin);
/* namei.c */
extern const struct inode_operations ext4_dir_inode_operations;
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 5313ae4..f2e2d57 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -129,8 +129,45 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
return dquot_file_open(inode, filp);
}
+loff_t ext4_llseek(struct file *file, loff_t offset, int origin)
+{
+ struct inode *inode = file->f_mapping->host;
+ loff_t maxbytes;
+
+ mutex_lock(&inode->i_mutex);
+ if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
+ maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
+ else
+ maxbytes = inode->i_sb->s_maxbytes;
+ switch (origin) {
+ case SEEK_END:
+ offset += inode->i_size;
+ break;
+ case SEEK_CUR:
+ if (offset == 0) {
+ mutex_unlock(&inode->i_mutex);
+ return file->f_pos;
+ }
+ offset += file->f_pos;
+ break;
+ }
+
+ if (offset < 0 || offset > maxbytes) {
+ mutex_unlock(&inode->i_mutex);
+ return -EINVAL;
+ }
+
+ if (offset != file->f_pos) {
+ file->f_pos = offset;
+ file->f_version = 0;
+ }
+ mutex_unlock(&inode->i_mutex);
+
+ return offset;
+}
+
const struct file_operations ext4_file_operations = {
- .llseek = generic_file_llseek,
+ .llseek = ext4_llseek,
.read = do_sync_read,
.write = do_sync_write,
.aio_read = generic_file_aio_read,
Hi. I have tested the following cases in order to confirm the maximum file size. For the tests, I selected two parameters: (These parameters relate to the max file size.) 1) Filesystem Feature "extent" 2) File(Inode) Flag "EXT4_EXTENTS_FL" (This parameter corresponds to the case where people shifts from ext3 into ext4. (Files which are created with ext3 have no "EXT4_EXTENTS_FL" flag.)) Table. the max file size which we can write or seek at each filesystem feature tuning and file flag setting +============+===============================+===============================+ | \ File flag| | | | \ | !EXT4_EXTENTS_FL | EXT4_EXTETNS_FL | |Fs Features\| | | +------------+-------------------------------+-------------------------------+ | !extent | write: 2194719883264 | write: -------------- | | | seek: 2199023251456 | seek: -------------- | +------------+-------------------------------+-------------------------------+ | extent | write: 4402345721856 | write: 17592186044415 | | | seek: 17592186044415 | seek: 17592186044415 | +------------+-------------------------------+-------------------------------+ ( The symbols (!extent, extent) mean: !extent: The filesystem feature "extent" is not set. ex. mkfs.ext3 <dev>; mount -t ext4 <dev> extent: The filesystem feature "extent" is set. ex. mkfs.ext3 <dev>; tune2fs -Oextent,huge_file <dev>; mount -t ext4 <dev> The symbols ("!EXT4_EXTENTS_FL","EXT4_EXTENTS_FL") mean: !EXT4_EXTENS_FL: The file flag, "EXT4_EXTENTS_FL" is not set. EXT4_EXTENS_FL: The file flag, "EXT4_EXTENTS_FL" is set. ) According to the table, if EXT4_EXTETNS_FL flag is not set, the max file size of write() is different from the one of seek(). These differences don't include in the ext4-specification, do they? I think the differences are not the ext4-specification. So, I made a fix patch of the differences.