[PATCH 1/2] xfs: Introduce XFS_EXTENT_BUSY_IN_TRANS busy extent flag

Chandan Babu R
2021-04-28T06:52:14Z

This commit adds the busy extent flag XFS_EXTENT_BUSY_IN_TRANS which can be
used to check if a busy extent is still on a transaction's t_busy list. The
flag will be set when an extent is freed by __xfs_free_extent() and it is
cleared when the busy extent is moved to CIL's busy extent list.

This flag will be used in a future commit to prevent a deadlock when
populating an AG's AGFL.

Signed-off-by: Chandan Babu R <chandanrlinux@gmail.com>
---
fs/xfs/libxfs/xfs_alloc.c | 2 +-
fs/xfs/xfs_extent_busy.h | 1 +
fs/xfs/xfs_log_cil.c | 4 ++++
3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index aaa19101bb2a..7dc50a435cf4 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -3332,7 +3332,7 @@ __xfs_free_extent(
xfs_agblock_t agbno = XFS_FSB_TO_AGBNO(mp, bno);
struct xfs_agf *agf;
int error;
- unsigned int busy_flags = 0;
+ unsigned int busy_flags = XFS_EXTENT_BUSY_IN_TRANS;

ASSERT(len != 0);
ASSERT(type != XFS_AG_RESV_AGFL);
diff --git a/fs/xfs/xfs_extent_busy.h b/fs/xfs/xfs_extent_busy.h
index 8aea07100092..929f72d1c699 100644
--- a/fs/xfs/xfs_extent_busy.h
+++ b/fs/xfs/xfs_extent_busy.h
@@ -28,6 +28,7 @@ struct xfs_extent_busy {
unsigned int flags;
#define XFS_EXTENT_BUSY_DISCARDED 0x01 /* undergoing a discard op. */
#define XFS_EXTENT_BUSY_SKIP_DISCARD 0x02 /* do not discard */
+#define XFS_EXTENT_BUSY_IN_TRANS 0x04
};

void
diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index b0ef071b3cb5..f91b69e92b85 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -390,6 +390,7 @@ xlog_cil_insert_items(
struct xfs_cil *cil = log->l_cilp;
struct xfs_cil_ctx *ctx = cil->xc_ctx;
struct xfs_log_item *lip;
+ struct xfs_extent_busy *busy;
int len = 0;
int diff_iovecs = 0;
int iclog_space;
@@ -410,6 +411,9 @@ xlog_cil_insert_items(
len += iovhdr_res;
ctx->nvecs += diff_iovecs;

+ list_for_each_entry(busy, &tp->t_busy, list)
+ busy->flags &= ~XFS_EXTENT_BUSY_IN_TRANS;
+
/* attach the transaction to the CIL if it has any busy extents */
if (!list_empty(&tp->t_busy))
list_splice_init(&tp->t_busy, &ctx->busy_extents);
--
2.30.2