5.15-stable review patch. If anyone has any objections, please let me know.
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From: Dai Ngo dai.ngo@oracle.com
[ Upstream commit 2443da2259e97688f93d64d17ab69b15f466078a ]
Add 2 new callbacks, lm_lock_expirable and lm_expire_lock, to lock_manager_operations to allow the lock manager to take appropriate action to resolve the lock conflict if possible.
A new field, lm_mod_owner, is also added to lock_manager_operations. The lm_mod_owner is used by the fs/lock code to make sure the lock manager module such as nfsd, is not freed while lock conflict is being resolved.
lm_lock_expirable checks and returns true to indicate that the lock conflict can be resolved else return false. This callback must be called with the flc_lock held so it can not block.
lm_expire_lock is called to resolve the lock conflict if the returned value from lm_lock_expirable is true. This callback is called without the flc_lock held since it's allowed to block. Upon returning from this callback, the lock conflict should be resolved and the caller is expected to restart the conflict check from the beginnning of the list.
Lock manager, such as NFSv4 courteous server, uses this callback to resolve conflict by destroying lock owner, or the NFSv4 courtesy client (client that has expired but allowed to maintains its states) that owns the lock.
Reviewed-by: J. Bruce Fields bfields@fieldses.org Signed-off-by: Dai Ngo dai.ngo@oracle.com Signed-off-by: Chuck Lever chuck.lever@oracle.com Reviewed-by: Jeff Layton jlayton@kernel.org Signed-off-by: Chuck Lever chuck.lever@oracle.com --- Documentation/filesystems/locking.rst | 4 ++++ fs/locks.c | 33 ++++++++++++++++++++++++--- include/linux/fs.h | 3 +++ 3 files changed, 37 insertions(+), 3 deletions(-)
diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index e2a27bb5dc411..dabf4f7c755ed 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -442,6 +442,8 @@ prototypes:: void (*lm_break)(struct file_lock *); /* break_lease callback */ int (*lm_change)(struct file_lock **, int); bool (*lm_breaker_owns_lease)(struct file_lock *); + bool (*lm_lock_expirable)(struct file_lock *); + void (*lm_expire_lock)(void);
locking rules:
@@ -453,6 +455,8 @@ lm_grant: no no no lm_break: yes no no lm_change yes no no lm_breaker_owns_lease: yes no no +lm_lock_expirable yes no no +lm_expire_lock no no yes ====================== ============= ================= =========
buffer_head diff --git a/fs/locks.c b/fs/locks.c index f8c4844ebcce4..317c2ec17b943 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -982,6 +982,8 @@ posix_test_lock(struct file *filp, struct file_lock *fl) struct file_lock *cfl; struct file_lock_context *ctx; struct inode *inode = locks_inode(filp); + void *owner; + void (*func)(void);
ctx = smp_load_acquire(&inode->i_flctx); if (!ctx || list_empty_careful(&ctx->flc_posix)) { @@ -989,12 +991,23 @@ posix_test_lock(struct file *filp, struct file_lock *fl) return; }
+retry: spin_lock(&ctx->flc_lock); list_for_each_entry(cfl, &ctx->flc_posix, fl_list) { - if (posix_locks_conflict(fl, cfl)) { - locks_copy_conflock(fl, cfl); - goto out; + if (!posix_locks_conflict(fl, cfl)) + continue; + if (cfl->fl_lmops && cfl->fl_lmops->lm_lock_expirable + && (*cfl->fl_lmops->lm_lock_expirable)(cfl)) { + owner = cfl->fl_lmops->lm_mod_owner; + func = cfl->fl_lmops->lm_expire_lock; + __module_get(owner); + spin_unlock(&ctx->flc_lock); + (*func)(); + module_put(owner); + goto retry; } + locks_copy_conflock(fl, cfl); + goto out; } fl->fl_type = F_UNLCK; out: @@ -1168,6 +1181,8 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, int error; bool added = false; LIST_HEAD(dispose); + void *owner; + void (*func)(void);
ctx = locks_get_lock_context(inode, request->fl_type); if (!ctx) @@ -1186,6 +1201,7 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, new_fl2 = locks_alloc_lock(); }
+retry: percpu_down_read(&file_rwsem); spin_lock(&ctx->flc_lock); /* @@ -1197,6 +1213,17 @@ static int posix_lock_inode(struct inode *inode, struct file_lock *request, list_for_each_entry(fl, &ctx->flc_posix, fl_list) { if (!posix_locks_conflict(request, fl)) continue; + if (fl->fl_lmops && fl->fl_lmops->lm_lock_expirable + && (*fl->fl_lmops->lm_lock_expirable)(fl)) { + owner = fl->fl_lmops->lm_mod_owner; + func = fl->fl_lmops->lm_expire_lock; + __module_get(owner); + spin_unlock(&ctx->flc_lock); + percpu_up_read(&file_rwsem); + (*func)(); + module_put(owner); + goto retry; + } if (conflock) locks_copy_conflock(conflock, fl); error = -EAGAIN; diff --git a/include/linux/fs.h b/include/linux/fs.h index 9b7ce642d4f08..371d67c9221c5 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1066,6 +1066,7 @@ struct file_lock_operations { };
struct lock_manager_operations { + void *lm_mod_owner; fl_owner_t (*lm_get_owner)(fl_owner_t); void (*lm_put_owner)(fl_owner_t); void (*lm_notify)(struct file_lock *); /* unblock callback */ @@ -1074,6 +1075,8 @@ struct lock_manager_operations { int (*lm_change)(struct file_lock *, int, struct list_head *); void (*lm_setup)(struct file_lock *, void **); bool (*lm_breaker_owns_lease)(struct file_lock *); + bool (*lm_lock_expirable)(struct file_lock *cfl); + void (*lm_expire_lock)(void); };
struct lock_manager {