[PATCH 13/29] xfs: make xfs_trans_alloc() support nowait semantics

Hao Xu
2023-08-25T14:01:40Z

There are locks in xfs_trans_alloc(), spot them and apply trylock logic.
Make them return -EAGAIN when it would block. To achieve this, add
nowait parameter for those functions in the path. Besides, add a generic
transaction flag XFS_TRANS_NOWAIT to deliver nowait info.

Signed-off-by: Hao Xu <howeyxu@tencent.com>
---
fs/xfs/libxfs/xfs_shared.h | 2 ++
fs/xfs/xfs_iops.c | 3 ++-
fs/xfs/xfs_trans.c | 21 ++++++++++++++++++---
3 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_shared.h b/fs/xfs/libxfs/xfs_shared.h
index c4381388c0c1..0ba3d6f53405 100644
--- a/fs/xfs/libxfs/xfs_shared.h
+++ b/fs/xfs/libxfs/xfs_shared.h
@@ -83,6 +83,8 @@ void xfs_log_get_max_trans_res(struct xfs_mount *mp,
* made then this algorithm will eventually find all the space it needs.
*/
#define XFS_TRANS_LOWMODE 0x100 /* allocate in low space mode */
+/* Transaction should follow nowait semantics */
+#define XFS_TRANS_NOWAIT (1u << 9)

/*
* Field values for xfs_trans_mod_sb.
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 5fa391083de9..47b4fd5f8f5c 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1054,7 +1054,8 @@ xfs_vn_update_time(
if (nowait)
old_pflags = memalloc_noio_save();

- error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0, 0, &tp);
+ error = xfs_trans_alloc(mp, &M_RES(mp)->tr_fsyncts, 0, 0,
+ nowait ? XFS_TRANS_NOWAIT : 0, &tp);
if (error)
goto out;

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 8c0bfc9a33b1..dbec685f4f4a 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -251,6 +251,9 @@ xfs_trans_alloc(
struct xfs_trans *tp;
bool want_retry = true;
int error;
+ bool nowait = flags & XFS_TRANS_NOWAIT;
+ gfp_t gfp_flags = GFP_KERNEL |
+ (nowait ? 0 : __GFP_NOFAIL);

/*
* Allocate the handle before we do our freeze accounting and setting up
@@ -258,9 +261,21 @@ xfs_trans_alloc(
* by doing GFP_KERNEL allocations inside sb_start_intwrite().
*/
retry:
- tp = kmem_cache_zalloc(xfs_trans_cache, GFP_KERNEL | __GFP_NOFAIL);
- if (!(flags & XFS_TRANS_NO_WRITECOUNT))
- sb_start_intwrite(mp->m_super);
+ tp = kmem_cache_zalloc(xfs_trans_cache, gfp_flags);
+ if (!tp)
+ return -EAGAIN;
+ if (!(flags & XFS_TRANS_NO_WRITECOUNT)) {
+ if (nowait) {
+ bool locked = sb_start_intwrite_trylock(mp->m_super);
+
+ if (!locked) {
+ xfs_trans_cancel(tp);
+ return -EAGAIN;
+ }
+ } else {
+ sb_start_intwrite(mp->m_super);
+ }
+ }
xfs_trans_set_context(tp);

/*
--
2.25.1