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fs: invalidate page cache after end_io() in dio completion

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Commit 332391a993 ("fs: Fix page cache inconsistency when mixing
buffered and AIO DIO") moved page cache invalidation from
iomap_dio_rw() to iomap_dio_complete() for iomap based direct write
path, but before the dio->end_io() call, and it re-introdued the bug
fixed by commit c771c14baa ("iomap: invalidate page caches should
be after iomap_dio_complete() in direct write").

I found this because fstests generic/418 started failing on XFS with
v4.14-rc3 kernel, which is the regression test for this specific
bug.

So similarly, fix it by moving dio->end_io() (which does the
unwritten extent conversion) before page cache invalidation, to make
sure next buffer read reads the final real allocations not unwritten
extents. I also add some comments about why should end_io() go first
in case we get it wrong again in the future.

Note that, there's no such problem in the non-iomap based direct
write path, because we didn't remove the page cache invalidation
after the ->direct_IO() in generic_file_direct_write() call, but I
decided to fix dio_complete() too so we don't leave a landmine
there, also be consistent with iomap_dio_complete().

Fixes: 332391a993 ("fs: Fix page cache inconsistency when mixing buffered and AIO DIO")
Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
This commit is contained in:
Eryu Guan 2017-10-13 09:47:46 -07:00 committed by Darrick J. Wong
parent 793d7dbe6d
commit 5e25c269e1
2 changed files with 36 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
fs/direct-io.c
View File

@ -259,12 +259,24 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
if (ret == 0)
ret = transferred;
if (dio->end_io) {
// XXX: ki_pos??
err = dio->end_io(dio->iocb, offset, ret, dio->private);
if (err)
ret = err;
}
/*
* Try again to invalidate clean pages which might have been cached by
* non-direct readahead, or faulted in by get_user_pages() if the source
* of the write was an mmap'ed region of the file we're writing. Either
* one is a pretty crazy thing to do, so we don't support it 100%. If
* this invalidation fails, tough, the write still worked...
*
* And this page cache invalidation has to be after dio->end_io(), as
* some filesystems convert unwritten extents to real allocations in
* end_io() when necessary, otherwise a racing buffer read would cache
* zeros from unwritten extents.
*/
if (ret > 0 && dio->op == REQ_OP_WRITE &&
dio->inode->i_mapping->nrpages) {
@ -274,14 +286,6 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
WARN_ON_ONCE(err);
}
if (dio->end_io) {
// XXX: ki_pos??
err = dio->end_io(dio->iocb, offset, ret, dio->private);
if (err)
ret = err;
}
if (!(dio->flags & DIO_SKIP_DIO_COUNT))
inode_dio_end(dio->inode);

41
fs/iomap.c
View File

@ -714,23 +714,9 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
struct kiocb *iocb = dio->iocb;
struct inode *inode = file_inode(iocb->ki_filp);
loff_t offset = iocb->ki_pos;
ssize_t ret;
/*
* Try again to invalidate clean pages which might have been cached by
* non-direct readahead, or faulted in by get_user_pages() if the source
* of the write was an mmap'ed region of the file we're writing. Either
* one is a pretty crazy thing to do, so we don't support it 100%. If
* this invalidation fails, tough, the write still worked...
*/
if (!dio->error &&
(dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
ret = invalidate_inode_pages2_range(inode->i_mapping,
iocb->ki_pos >> PAGE_SHIFT,
(iocb->ki_pos + dio->size - 1) >> PAGE_SHIFT);
WARN_ON_ONCE(ret);
}
if (dio->end_io) {
ret = dio->end_io(iocb,
dio->error ? dio->error : dio->size,
@ -742,12 +728,33 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
if (likely(!ret)) {
ret = dio->size;
/* check for short read */
if (iocb->ki_pos + ret > dio->i_size &&
if (offset + ret > dio->i_size &&
!(dio->flags & IOMAP_DIO_WRITE))
ret = dio->i_size - iocb->ki_pos;
ret = dio->i_size - offset;
iocb->ki_pos += ret;
}
/*
* Try again to invalidate clean pages which might have been cached by
* non-direct readahead, or faulted in by get_user_pages() if the source
* of the write was an mmap'ed region of the file we're writing. Either
* one is a pretty crazy thing to do, so we don't support it 100%. If
* this invalidation fails, tough, the write still worked...
*
* And this page cache invalidation has to be after dio->end_io(), as
* some filesystems convert unwritten extents to real allocations in
* end_io() when necessary, otherwise a racing buffer read would cache
* zeros from unwritten extents.
*/
if (!dio->error &&
(dio->flags & IOMAP_DIO_WRITE) && inode->i_mapping->nrpages) {
int err;
err = invalidate_inode_pages2_range(inode->i_mapping,
offset >> PAGE_SHIFT,
(offset + dio->size - 1) >> PAGE_SHIFT);
WARN_ON_ONCE(err);
}
inode_dio_end(file_inode(iocb->ki_filp));
kfree(dio);