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ext3: Add replace-on-truncate hueristics for data=writeback mode

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In data=writeback mode, start an asynchronous flush when closing a
file which had been previously truncated down to zero.  This lowers
the probability of data loss in the case of applications that attempt
to replace a file using truncate.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2009-04-03 01:34:35 -04:00
commit f7ab34ea72
3 changed files with 8 additions and 0 deletions
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4
fs/ext3/file.c
View file

@ -33,6 +33,10 @@
*/ */
static int ext3_release_file (struct inode * inode, struct file * filp) static int ext3_release_file (struct inode * inode, struct file * filp)
{ {
if (EXT3_I(inode)->i_state & EXT3_STATE_FLUSH_ON_CLOSE) {
filemap_flush(inode->i_mapping);
EXT3_I(inode)->i_state &= ~EXT3_STATE_FLUSH_ON_CLOSE;
}
/* if we are the last writer on the inode, drop the block reservation */ /* if we are the last writer on the inode, drop the block reservation */
if ((filp->f_mode & FMODE_WRITE) && if ((filp->f_mode & FMODE_WRITE) &&
(atomic_read(&inode->i_writecount) == 1)) (atomic_read(&inode->i_writecount) == 1))

3
fs/ext3/inode.c
View file

@ -2346,6 +2346,9 @@ void ext3_truncate(struct inode *inode)
if (!ext3_can_truncate(inode)) if (!ext3_can_truncate(inode))
return; return;
if (inode->i_size == 0 && ext3_should_writeback_data(inode))
ei->i_state |= EXT3_STATE_FLUSH_ON_CLOSE;
/* /*
* We have to lock the EOF page here, because lock_page() nests * We have to lock the EOF page here, because lock_page() nests
* outside journal_start(). * outside journal_start().

1
include/linux/ext3_fs.h
View file

@ -208,6 +208,7 @@ static inline __u32 ext3_mask_flags(umode_t mode, __u32 flags)
#define EXT3_STATE_JDATA 0x00000001 /* journaled data exists */ #define EXT3_STATE_JDATA 0x00000001 /* journaled data exists */
#define EXT3_STATE_NEW 0x00000002 /* inode is newly created */ #define EXT3_STATE_NEW 0x00000002 /* inode is newly created */
#define EXT3_STATE_XATTR 0x00000004 /* has in-inode xattrs */ #define EXT3_STATE_XATTR 0x00000004 /* has in-inode xattrs */
#define EXT3_STATE_FLUSH_ON_CLOSE 0x00000008
/* Used to pass group descriptor data when online resize is done */ /* Used to pass group descriptor data when online resize is done */
struct ext3_new_group_input { struct ext3_new_group_input {