This is a note to let you know that I've just added the patch titled
xfs: reject all unaligned direct writes to reflinked files
to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xfs-reject-all-unaligned-direct-writes-to-reflinked-files.patch
and it can be found in the queue-4.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Mon, 6 Feb 2017 13:00:54 -0800
Subject: xfs: reject all unaligned direct writes to reflinked files
From: Christoph Hellwig <hch@xxxxxx>
commit 54a4ef8af4e0dc5c983d17fcb9cf5fd25666d94e upstream.
We currently fall back from direct to buffered writes if we detect a
remaining shared extent in the iomap_begin callback. But by the time
iomap_begin is called for the potentially unaligned end block we might
have already written most of the data to disk, which we'd now write
again using buffered I/O. To avoid this reject all writes to reflinked
files before starting I/O so that we are guaranteed to only write the
data once.
The alternative would be to unshare the unaligned start and/or end block
before doing the I/O. I think that's doable, and will actually be
required to support reflinks on DAX file system. But it will take a
little more time and I'd rather get rid of the double write ASAP.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/xfs/xfs_file.c | 9 +++++++++
fs/xfs/xfs_iomap.c | 12 +-----------
fs/xfs/xfs_trace.h | 2 +-
3 files changed, 11 insertions(+), 12 deletions(-)
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -527,6 +527,15 @@ xfs_file_dio_aio_write(
if ((iocb->ki_pos & mp->m_blockmask) ||
((iocb->ki_pos + count) & mp->m_blockmask)) {
unaligned_io = 1;
+
+ /*
+ * We can't properly handle unaligned direct I/O to reflink
+ * files yet, as we can't unshare a partial block.
+ */
+ if (xfs_is_reflink_inode(ip)) {
+ trace_xfs_reflink_bounce_dio_write(ip, iocb->ki_pos, count);
+ return -EREMCHG;
+ }
iolock = XFS_IOLOCK_EXCL;
} else {
iolock = XFS_IOLOCK_SHARED;
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1026,17 +1026,7 @@ xfs_file_iomap_begin(
if (error)
goto out_unlock;
- /*
- * We're here because we're trying to do a directio write to a
- * region that isn't aligned to a filesystem block. If the
- * extent is shared, fall back to buffered mode to handle the
- * RMW.
- */
- if (!(flags & IOMAP_REPORT) && shared) {
- trace_xfs_reflink_bounce_dio_write(ip, &imap);
- error = -EREMCHG;
- goto out_unlock;
- }
+ ASSERT((flags & IOMAP_REPORT) || !shared);
}
if ((flags & (IOMAP_WRITE | IOMAP_ZERO)) && xfs_is_reflink_inode(ip)) {
--- a/fs/xfs/xfs_trace.h
+++ b/fs/xfs/xfs_trace.h
@@ -3250,7 +3250,7 @@ DEFINE_INODE_IREC_EVENT(xfs_reflink_conv
DEFINE_RW_EVENT(xfs_reflink_reserve_cow);
DEFINE_RW_EVENT(xfs_reflink_allocate_cow_range);
-DEFINE_INODE_IREC_EVENT(xfs_reflink_bounce_dio_write);
+DEFINE_SIMPLE_IO_EVENT(xfs_reflink_bounce_dio_write);
DEFINE_IOMAP_EVENT(xfs_reflink_find_cow_mapping);
DEFINE_INODE_IREC_EVENT(xfs_reflink_trim_irec);
Patches currently in stable-queue which might be from hch@xxxxxx are
queue-4.10/xfs-mark-speculative-prealloc-cow-fork-extents-unwritten.patch
queue-4.10/xfs-fix-toctou-race-when-locking-an-inode-to-access-the-data-map.patch
queue-4.10/xfs-use-iomap-new-flag-for-newly-allocated-delalloc-blocks.patch
queue-4.10/xfs-reject-all-unaligned-direct-writes-to-reflinked-files.patch
queue-4.10/xfs-allow-unwritten-extents-in-the-cow-fork.patch
queue-4.10/xfs-tune-down-agno-asserts-in-the-bmap-code.patch
queue-4.10/xfs-verify-free-block-header-fields.patch
queue-4.10/xfs-check-for-obviously-bad-level-values-in-the-bmbt-root.patch
queue-4.10/xfs-don-t-fail-xfs_extent_busy-allocation.patch
queue-4.10/xfs-sync-eofblocks-scans-under-iolock-are-livelock-prone.patch
queue-4.10/xfs-pull-up-iolock-from-xfs_free_eofblocks.patch
queue-4.10/xfs-fail-_dir_open-when-readahead-fails.patch
queue-4.10/xfs-update-ctime-and-mtime-on-clone-destinatation-inodes.patch
queue-4.10/xfs-use-xfs_icluster_size_fsb-to-calculate-inode-chunk-alignment.patch
queue-4.10/xfs-only-reclaim-unwritten-cow-extents-periodically.patch
queue-4.10/xfs-try-any-ag-when-allocating-the-first-btree-block-when-reflinking.patch
queue-4.10/xfs-fix-and-streamline-error-handling-in-xfs_end_io.patch
queue-4.10/xfs-fix-eofblocks-race-with-file-extending-async-dio-writes.patch