From 5e25c269e17de4c5a23ce886cda612b01365a944 Mon Sep 17 00:00:00 2001 From: Eryu Guan Date: Fri, 13 Oct 2017 09:47:46 -0700 Subject: [PATCH] fs: invalidate page cache after end_io() in dio completion Commit 332391a9935d ("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 c771c14baa33 ("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: 332391a9935d ("fs: Fix page cache inconsistency when mixing buffered and AIO DIO") Signed-off-by: Eryu Guan Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Reviewed-by: Jan Kara Reviewed-by: Lukas Czerner --- fs/direct-io.c | 20 ++++++++++++-------- fs/iomap.c | 41 ++++++++++++++++++++++++----------------- 2 files changed, 36 insertions(+), 25 deletions(-) diff --git a/fs/direct-io.c b/fs/direct-io.c index 96415c65bbdc..19ac3fe57deb 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -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); diff --git a/fs/iomap.c b/fs/iomap.c index be61cf742b5e..d4801f8dd4fd 100644 --- a/fs/iomap.c +++ b/fs/iomap.c @@ -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); -- 2.30.2