[PATCH 5.15.y] xfs: mark the inode preallocated for pNFS write layouts past EOF

[Sasha Levin <sashal@kernel.org>]

From: Daejun Park <daejun7.park@samsung.com>

[ Upstream commit 8b8e265991556d99b6d721697f148975a7c68767 ]

xfs_fs_map_blocks() marks the inode XFS_DIFLAG_PREALLOC only when it
allocates blocks for a write layout. A write layout past EOF can also
hand out allocated blocks, such as speculative preallocation. blockgc
then frees them under the layout, and another file may get them.

Mark the inode whenever a write mapping ends past EOF.

Fixes: 527851124d10 ("xfs: implement pNFS export operations")
Cc: stable@vger.kernel.org
Reported-by: Chuck Lever <cel@kernel.org>
Link: https://lore.kernel.org/r/4de5356f-bc4d-4f1a-9c81-fce09b1b46fd@slotpi15m67
Signed-off-by: Daejun Park <daejun7.park@samsung.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
[ sashal: replaced xfs_fs_map_update_inode() with xfs_update_prealloc_flags(ip, XFS_PREALLOC_SET) ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/xfs/xfs_pnfs.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index 0bf547d730990..a8db739dd4166 100644
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -91,6 +91,7 @@ xfs_fs_map_blocks(
 	int			nimaps = 1;
 	uint			lock_flags;
 	int			error = 0;
+	bool			update_inode = false;
 
 	if (xfs_is_shutdown(mp))
 		return -EIO;
@@ -157,7 +158,24 @@ xfs_fs_map_blocks(
 				end_fsb - offset_fsb, &imap);
 		if (error)
 			goto out_unlock;
+		update_inode = true;
+	} else {
+		xfs_iunlock(ip, lock_flags);
 
+		/*
+		 * Blocks past EOF that were allocated for buffered writes, such
+		 * as speculative preallocation, can be freed by
+		 * xfs_free_eofblocks() without breaking the layout unless the
+		 * inode is marked as preallocated. Mark it before handing them
+		 * out for writing, as for blocks allocated above.
+		 */
+		if (!error && write && !(ip->i_diflags & XFS_DIFLAG_PREALLOC) &&
+		    imap.br_startoff + imap.br_blockcount >
+		    XFS_B_TO_FSB(mp, XFS_ISIZE(ip)))
+			update_inode = true;
+	}
+
+	if (update_inode) {
 		/*
 		 * Ensure the next transaction is committed synchronously so
 		 * that the blocks allocated and handed out to the client are
@@ -168,9 +186,6 @@ xfs_fs_map_blocks(
 			error = xfs_log_force_inode(ip);
 		if (error)
 			goto out_unlock;
-
-	} else {
-		xfs_iunlock(ip, lock_flags);
 	}
 	xfs_iunlock(ip, XFS_IOLOCK_EXCL);
 
-- 
2.53.0