Merge tag 'xfs-4.18-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux

Pull xfs fixes from Darrick Wong:
 "Here are some patches for 4.18 to fix regressions, accounting
  problems, overflow problems, and to strengthen metadata validation to
  prevent corruption.

  This series has been run through a full xfstests run over the weekend
  and through a quick xfstests run against this morning's master, with
  no major failures reported.

  Changes since last update:

   - more metadata validation strengthening to prevent crashes.

   - fix extent offset overflow problem when insert_range on a 512b
     block fs

   - fix some off-by-one errors in the realtime fsmap code

   - fix some math errors in the default resblks calculation when free
     space is low

   - fix a problem where stale page contents are exposed via mmap read
     after a zero_range at eof

   - fix accounting problems with per-ag reservations causing statfs
     reports to vary incorrectly"

* tag 'xfs-4.18-fixes-2' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
  xfs: fix fdblocks accounting w/ RMAPBT per-AG reservation
  xfs: ensure post-EOF zeroing happens after zeroing part of a file
  xfs: fix off-by-one error in xfs_rtalloc_query_range
  xfs: fix uninitialized field in rtbitmap fsmap backend
  xfs: recheck reflink state after grabbing ILOCK_SHARED for a write
  xfs: don't allow insert-range to shift extents past the maximum offset
  xfs: don't trip over negative free space in xfs_reserve_blocks
  xfs: allow empty transactions while frozen
  xfs: xfs_iflush_abort() can be called twice on cluster writeback failure
  xfs: More robust inode extent count validation
  xfs: simplify xfs_bmap_punch_delalloc_range

1 files changed, 14 insertions, 1 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 49f5492eed3b..55876dd02f0c 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -963,12 +963,13 @@ xfs_ilock_for_iomap(
 	unsigned		*lockmode)
 {
 	unsigned		mode = XFS_ILOCK_SHARED;
+	bool			is_write = flags & (IOMAP_WRITE | IOMAP_ZERO);
 
 	/*
 	 * COW writes may allocate delalloc space or convert unwritten COW
 	 * extents, so we need to make sure to take the lock exclusively here.
 	 */
-	if (xfs_is_reflink_inode(ip) && (flags & (IOMAP_WRITE | IOMAP_ZERO))) {
+	if (xfs_is_reflink_inode(ip) && is_write) {
 		/*
 		 * FIXME: It could still overwrite on unshared extents and not
 		 * need allocation.
@@ -989,6 +990,7 @@ xfs_ilock_for_iomap(
 		mode = XFS_ILOCK_EXCL;
 	}
 
+relock:
 	if (flags & IOMAP_NOWAIT) {
 		if (!xfs_ilock_nowait(ip, mode))
 			return -EAGAIN;
@@ -996,6 +998,17 @@ xfs_ilock_for_iomap(
 		xfs_ilock(ip, mode);
 	}
 
+	/*
+	 * The reflink iflag could have changed since the earlier unlocked
+	 * check, so if we got ILOCK_SHARED for a write and but we're now a
+	 * reflink inode we have to switch to ILOCK_EXCL and relock.
+	 */
+	if (mode == XFS_ILOCK_SHARED && is_write && xfs_is_reflink_inode(ip)) {
+		xfs_iunlock(ip, mode);
+		mode = XFS_ILOCK_EXCL;
+		goto relock;
+	}
+
 	*lockmode = mode;
 	return 0;
 }