xfs: ensure st_blocks never goes to zero during COW writes

COW writes remove the amount overwritten either directly for delalloc
reservations, or in earlier deferred transactions than adding the new
amount back in the bmap map transaction.  This means st_blocks on an
inode where all data is overwritten using the COW path can temporarily
show a 0 st_blocks.  This can easily be reproduced with the pending
zoned device support where all writes use this path and trips the
check in generic/615, but could also happen on a reflink file without
that.

Fix this by temporarily add the pending blocks to be mapped to
i_delayed_blks while the item is queued.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 28473b6a95cc7fe6d7579fa7e70d339d1f301a83..8090e8249116d0b24d506b495455b996be555eac 100644 (file)
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -4856,6 +4856,7 @@ xfs_bmapi_remap(
        }
 
        ip->i_nblocks += len;
+       ip->i_delayed_blks -= len; /* see xfs_bmap_defer_add */
        xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
 
        if (ifp->if_format == XFS_DINODE_FMT_BTREE)

diff --git a/fs/xfs/xfs_bmap_item.c b/fs/xfs/xfs_bmap_item.c
index e224b49b7cff6d6274c9c4611f6d4166185bc831..35a8c1b8b3cb34e3033ec21363fe71d9f9a1592d 100644 (file)
--- a/fs/xfs/xfs_bmap_item.c
+++ b/fs/xfs/xfs_bmap_item.c
@@ -346,6 +346,17 @@ xfs_bmap_defer_add(
        trace_xfs_bmap_defer(bi);
 
        xfs_bmap_update_get_group(tp->t_mountp, bi);
+
+       /*
+        * Ensure the deferred mapping is pre-recorded in i_delayed_blks.
+        *
+        * Otherwise stat can report zero blocks for an inode that actually has
+        * data when the entire mapping is in the process of being overwritten
+        * using the out of place write path. This is undone in xfs_bmapi_remap
+        * after it has incremented di_nblocks for a successful operation.
+        */
+       if (bi->bi_type == XFS_BMAP_MAP)
+               bi->bi_owner->i_delayed_blks += bi->bi_bmap.br_blockcount;
        xfs_defer_add(tp, &bi->bi_list, &xfs_bmap_update_defer_type);
 }
 
@@ -367,6 +378,9 @@ xfs_bmap_update_cancel_item(
 {
        struct xfs_bmap_intent          *bi = bi_entry(item);
 
+       if (bi->bi_type == XFS_BMAP_MAP)
+               bi->bi_owner->i_delayed_blks -= bi->bi_bmap.br_blockcount;
+
        xfs_bmap_update_put_group(bi);
        kmem_cache_free(xfs_bmap_intent_cache, bi);
 }
@@ -464,6 +478,9 @@ xfs_bui_recover_work(
        bi->bi_owner = *ipp;
        xfs_bmap_update_get_group(mp, bi);
 
+       /* see xfs_bmap_defer_add for details */
+       if (bi->bi_type == XFS_BMAP_MAP)
+               bi->bi_owner->i_delayed_blks += bi->bi_bmap.br_blockcount;
        xfs_defer_add_item(dfp, &bi->bi_list);
        return bi;
 }