Skip to content

Commit

Permalink
ext4: properly sync file size update after O_SYNC direct IO
Browse files Browse the repository at this point in the history 
commit 9156289 upstream.

Gao Xiang has reported that on ext4 O_SYNC direct IO does not properly
sync file size update and thus if we crash at unfortunate moment, the
file can have smaller size although O_SYNC IO has reported successful
completion. The problem happens because update of on-disk inode size is
handled in ext4_dio_write_iter() *after* iomap_dio_rw() (and thus
dio_complete() in particular) has returned and generic_file_sync() gets
called by dio_complete(). Fix the problem by handling on-disk inode size
update directly in our ->end_io completion handler.

References: https://lore.kernel.org/all/02d18236-26ef-09b0-90ad-030c4fe3ee20@linux.alibaba.com
Reported-by: Gao Xiang <hsiangkao@linux.alibaba.com>
CC: stable@vger.kernel.org
Fixes: 378f32b ("ext4: introduce direct I/O write using iomap infrastructure")
Signed-off-by: Jan Kara <jack@suse.cz>
Tested-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: "Ritesh Harjani (IBM)" <ritesh.list@gmail.com>
Link: https://lore.kernel.org/r/20231013121350.26872-1-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  • Loading branch information
@jankara @gregkh
jankara authored and gregkh committed Nov 28, 2023
1 parent e1d0f68 commit dc45428
Showing 1 changed file with 65 additions and 88 deletions.
153 changes: 65 additions & 88 deletions fs/ext4/file.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -296,80 +296,38 @@ static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
}

static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
ssize_t written, size_t count)
ssize_t count)
{
handle_t *handle;
bool truncate = false;
u8 blkbits = inode->i_blkbits;
ext4_lblk_t written_blk, end_blk;
int ret;

/*
* Note that EXT4_I(inode)->i_disksize can get extended up to
* inode->i_size while the I/O was running due to writeback of delalloc
* blocks. But, the code in ext4_iomap_alloc() is careful to use
* zeroed/unwritten extents if this is possible; thus we won't leave
* uninitialized blocks in a file even if we didn't succeed in writing
* as much as we intended.
*/
WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize);
if (offset + count <= EXT4_I(inode)->i_disksize) {
/*
* We need to ensure that the inode is removed from the orphan
* list if it has been added prematurely, due to writeback of
* delalloc blocks.
*/
if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) {
handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);

if (IS_ERR(handle)) {
ext4_orphan_del(NULL, inode);
return PTR_ERR(handle);
}

ext4_orphan_del(handle, inode);
ext4_journal_stop(handle);
}

return written;
}

if (written < 0)
goto truncate;

lockdep_assert_held_write(&inode->i_rwsem);
handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
if (IS_ERR(handle)) {
written = PTR_ERR(handle);
goto truncate;
}
if (IS_ERR(handle))
return PTR_ERR(handle);

if (ext4_update_inode_size(inode, offset + written)) {
ret = ext4_mark_inode_dirty(handle, inode);
if (ext4_update_inode_size(inode, offset + count)) {
int ret = ext4_mark_inode_dirty(handle, inode);
if (unlikely(ret)) {
written = ret;
ext4_journal_stop(handle);
goto truncate;
return ret;
}
}

/*
* We may need to truncate allocated but not written blocks beyond EOF.
*/
written_blk = ALIGN(offset + written, 1 << blkbits);
end_blk = ALIGN(offset + count, 1 << blkbits);
if (written_blk < end_blk && ext4_can_truncate(inode))
truncate = true;

/*
* Remove the inode from the orphan list if it has been extended and
* everything went OK.
*/
if (!truncate && inode->i_nlink)
if (inode->i_nlink)
ext4_orphan_del(handle, inode);
ext4_journal_stop(handle);

if (truncate) {
truncate:
return count;
}

/*
* Clean up the inode after DIO or DAX extending write has completed and the
* inode size has been updated using ext4_handle_inode_extension().
*/
static void ext4_inode_extension_cleanup(struct inode *inode, ssize_t count)
{
lockdep_assert_held_write(&inode->i_rwsem);
if (count < 0) {
ext4_truncate_failed_write(inode);
/*
* If the truncate operation failed early, then the inode may
Expand All @@ -378,9 +336,28 @@ static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
*/
if (inode->i_nlink)
ext4_orphan_del(NULL, inode);
return;
}
/*
* If i_disksize got extended due to writeback of delalloc blocks while
* the DIO was running we could fail to cleanup the orphan list in
* ext4_handle_inode_extension(). Do it now.
*/
if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) {
handle_t *handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);

return written;
if (IS_ERR(handle)) {
/*
* The write has successfully completed. Not much to
* do with the error here so just cleanup the orphan
* list and hope for the best.
*/
ext4_orphan_del(NULL, inode);
return;
}
ext4_orphan_del(handle, inode);
ext4_journal_stop(handle);
}
}

static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
Expand All @@ -389,31 +366,22 @@ static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
loff_t pos = iocb->ki_pos;
struct inode *inode = file_inode(iocb->ki_filp);

if (!error && size && flags & IOMAP_DIO_UNWRITTEN)
error = ext4_convert_unwritten_extents(NULL, inode, pos, size);
if (error)
return error;

if (size && flags & IOMAP_DIO_UNWRITTEN) {
error = ext4_convert_unwritten_extents(NULL, inode, pos, size);
if (error < 0)
return error;
}
/*
* If we are extending the file, we have to update i_size here before
* page cache gets invalidated in iomap_dio_rw(). Otherwise racing
* buffered reads could zero out too much from page cache pages. Update
* of on-disk size will happen later in ext4_dio_write_iter() where
* we have enough information to also perform orphan list handling etc.
* Note that we perform all extending writes synchronously under
* i_rwsem held exclusively so i_size update is safe here in that case.
* If the write was not extending, we cannot see pos > i_size here
* because operations reducing i_size like truncate wait for all
* outstanding DIO before updating i_size.
* Note that EXT4_I(inode)->i_disksize can get extended up to
* inode->i_size while the I/O was running due to writeback of delalloc
* blocks. But the code in ext4_iomap_alloc() is careful to use
* zeroed/unwritten extents if this is possible; thus we won't leave
* uninitialized blocks in a file even if we didn't succeed in writing
* as much as we intended.
*/
pos += size;
if (pos > i_size_read(inode))
i_size_write(inode, pos);

return 0;
WARN_ON_ONCE(i_size_read(inode) < READ_ONCE(EXT4_I(inode)->i_disksize));
if (pos + size <= READ_ONCE(EXT4_I(inode)->i_disksize))
return size;
return ext4_handle_inode_extension(inode, pos, size);
}

static const struct iomap_dio_ops ext4_dio_write_ops = {
Expand Down Expand Up @@ -589,9 +557,16 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
NULL, 0);
if (ret == -ENOTBLK)
ret = 0;

if (extend)
ret = ext4_handle_inode_extension(inode, offset, ret, count);
if (extend) {
/*
* We always perform extending DIO write synchronously so by
* now the IO is completed and ext4_handle_inode_extension()
* was called. Cleanup the inode in case of error or race with
* writeback of delalloc blocks.
*/
WARN_ON_ONCE(ret == -EIOCBQUEUED);
ext4_inode_extension_cleanup(inode, ret);
}

out:
if (ilock_shared)
Expand Down Expand Up @@ -672,8 +647,10 @@ ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)

ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);

if (extend)
ret = ext4_handle_inode_extension(inode, offset, ret, count);
if (extend) {
ret = ext4_handle_inode_extension(inode, offset, ret);
ext4_inode_extension_cleanup(inode, ret);
}
out:
inode_unlock(inode);
if (ret > 0)
Expand Down

0 comments on commit dc45428

Please sign in to comment.