xfs: Fix dax inode extent calculation when direct write is performed on an unwritten...

With dax enabled filesystems, a direct write operation into an existing
unwritten extent results in xfs_iomap_write_direct() zero-ing and converting
the extent into a normal extent before the actual data is copied from the
userspace buffer.

The inode extent count can increase by 2 if the extent range being written to
maps to the middle of the existing unwritten extent range. Hence this commit
uses XFS_IEXT_WRITE_UNWRITTEN_CNT as the extent count delta when such a write
operation is being performed.

Fixes: 727e1acd297c ("xfs: Check for extent overflow when trivally adding a new extent")
Reported-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index e17ab7f42928a55738f031a30111a4be86ae388a..8b27c10a3d085eaae3e6c71b1fcd84f1e0a958a8 100644 (file)
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -198,6 +198,7 @@ xfs_iomap_write_direct(
        bool                    force = false;
        int                     error;
        int                     bmapi_flags = XFS_BMAPI_PREALLOC;
+       int                     nr_exts = XFS_IEXT_ADD_NOSPLIT_CNT;
 
        ASSERT(count_fsb > 0);
 
@@ -232,6 +233,7 @@ xfs_iomap_write_direct(
                bmapi_flags = XFS_BMAPI_CONVERT | XFS_BMAPI_ZERO;
                if (imap->br_state == XFS_EXT_UNWRITTEN) {
                        force = true;
+                       nr_exts = XFS_IEXT_WRITE_UNWRITTEN_CNT;
                        dblocks = XFS_DIOSTRAT_SPACE_RES(mp, 0) << 1;
                }
        }
@@ -241,8 +243,7 @@ xfs_iomap_write_direct(
        if (error)
                return error;
 
-       error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK,
-                       XFS_IEXT_ADD_NOSPLIT_CNT);
+       error = xfs_iext_count_may_overflow(ip, XFS_DATA_FORK, nr_exts);
        if (error)
                goto out_trans_cancel;