[PATCH 04/13] xfs: move RT inode locking out of __xfs_bunmapi

Christoph Hellwig
2024-03-27T11:03:38Z

__xfs_bunmapi is a bit of an odd place to lock the rtbitmap and rtsummary
inodes given that it is very high level code. While this only looks ugly
right now, it will become a problem when supporting delayed allocations
for RT inodes as __xfs_bunmapi might end up deleting only delalloc extents
and thus never unlock the rt inodes.

Move the locking into xfs_bmap_del_extent_real just before the call to
xfs_rtfree_blocks instead and use a new flag in the transaction to ensure
that the locking happens only once.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/xfs/libxfs/xfs_bmap.c | 15 ++++++++-------
fs/xfs/libxfs/xfs_shared.h | 3 +++
2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 282b44deb9f864..e5e199d325982f 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5305,6 +5305,14 @@ xfs_bmap_del_extent_real(
if (xfs_is_reflink_inode(ip) && whichfork == XFS_DATA_FORK) {
xfs_refcount_decrease_extent(tp, del);
} else if (xfs_ifork_is_realtime(ip, whichfork)) {
+ /*
+ * Ensure the bitmap and summary inodes are locked
+ * and joined to the transaction before modifying them.
+ */
+ if (!(tp->t_flags & XFS_TRANS_RTBITMAP_LOCKED)) {
+ tp->t_flags |= XFS_TRANS_RTBITMAP_LOCKED;
+ xfs_rtbitmap_lock(tp, mp);
+ }
error = xfs_rtfree_blocks(tp, del->br_startblock,
del->br_blockcount);
} else {
@@ -5406,13 +5414,6 @@ __xfs_bunmapi(
} else
cur = NULL;

- if (isrt) {
- /*
- * Synchronize by locking the realtime bitmap.
- */
- xfs_rtbitmap_lock(tp, mp);
- }
-
extno = 0;
while (end != (xfs_fileoff_t)-1 && end >= start &&
(nexts == 0 || extno < nexts)) {
diff --git a/fs/xfs/libxfs/xfs_shared.h b/fs/xfs/libxfs/xfs_shared.h
index f35640ad3e7fe4..34f104ed372c09 100644
--- a/fs/xfs/libxfs/xfs_shared.h
+++ b/fs/xfs/libxfs/xfs_shared.h
@@ -137,6 +137,9 @@ void xfs_log_get_max_trans_res(struct xfs_mount *mp,
*/
#define XFS_TRANS_LOWMODE (1u << 8)

+/* Transaction has locked the rtbitmap and rtsum inodes */
+#define XFS_TRANS_RTBITMAP_LOCKED (1u << 9)
+
/*
* Field values for xfs_trans_mod_sb.
*/
--
2.39.2