CIFS: Turn lock mutex into rw semaphore

and allow several processes to walk through the lock list and read
can_cache_brlcks value if they are not going to modify them.

Signed-off-by: Pavel Shilovsky <pshilovsky@etersoft.ru>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 31 insertions, 29 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index e2a8e4456275..1adff75dfffc 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -260,9 +260,9 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
         INIT_LIST_HEAD(&fdlocks->locks);
         fdlocks->cfile = cfile;
         cfile->llist = fdlocks;
-        mutex_lock(&cinode->lock_mutex);
+        down_write(&cinode->lock_sem);
         list_add(&fdlocks->llist, &cinode->llist);
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
 
         cfile->count = 1;
         cfile->pid = current->tgid;
@@ -351,7 +351,7 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
          * Delete any outstanding lock records. We'll lose them when the file
          * is closed anyway.
          */
-        mutex_lock(&cifsi->lock_mutex);
+        down_write(&cifsi->lock_sem);
         list_for_each_entry_safe(li, tmp, &cifs_file->llist->locks, llist) {
                 list_del(&li->llist);
                 cifs_del_lock_waiters(li);
@@ -359,7 +359,7 @@ void cifsFileInfo_put(struct cifsFileInfo *cifs_file)
         }
         list_del(&cifs_file->llist->llist);
         kfree(cifs_file->llist);
-        mutex_unlock(&cifsi->lock_mutex);
+        up_write(&cifsi->lock_sem);
 
         cifs_put_tlink(cifs_file->tlink);
         dput(cifs_file->dentry);
@@ -762,7 +762,7 @@ cifs_lock_test(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
         struct TCP_Server_Info *server = tlink_tcon(cfile->tlink)->ses->server;
         bool exist;
 
-        mutex_lock(&cinode->lock_mutex);
+        down_read(&cinode->lock_sem);
 
         exist = cifs_find_lock_conflict(cfile, offset, length, type,
                                         &conf_lock);
@@ -779,7 +779,7 @@ cifs_lock_test(struct cifsFileInfo *cfile, __u64 offset, __u64 length,
         else
                 flock->fl_type = F_UNLCK;
 
-        mutex_unlock(&cinode->lock_mutex);
+        up_read(&cinode->lock_sem);
         return rc;
 }
 
@@ -787,9 +787,9 @@ static void
 cifs_lock_add(struct cifsFileInfo *cfile, struct cifsLockInfo *lock)
 {
         struct cifsInodeInfo *cinode = CIFS_I(cfile->dentry->d_inode);
-        mutex_lock(&cinode->lock_mutex);
+        down_write(&cinode->lock_sem);
         list_add_tail(&lock->llist, &cfile->llist->locks);
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
 }
 
 /*
@@ -809,13 +809,13 @@ cifs_lock_add_if(struct cifsFileInfo *cfile, struct cifsLockInfo *lock,
 
 try_again:
         exist = false;
-        mutex_lock(&cinode->lock_mutex);
+        down_write(&cinode->lock_sem);
 
         exist = cifs_find_lock_conflict(cfile, lock->offset, lock->length,
                                         lock->type, &conf_lock);
         if (!exist && cinode->can_cache_brlcks) {
                 list_add_tail(&lock->llist, &cfile->llist->locks);
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 return rc;
         }
 
@@ -825,17 +825,17 @@ try_again:
                 rc = -EACCES;
         else {
                 list_add_tail(&lock->blist, &conf_lock->blist);
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 rc = wait_event_interruptible(lock->block_q,
                                         (lock->blist.prev == &lock->blist) &&
                                         (lock->blist.next == &lock->blist));
                 if (!rc)
                         goto try_again;
-                mutex_lock(&cinode->lock_mutex);
+                down_write(&cinode->lock_sem);
                 list_del_init(&lock->blist);
         }
 
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
         return rc;
 }
 
@@ -856,7 +856,7 @@ cifs_posix_lock_test(struct file *file, struct file_lock *flock)
         if ((flock->fl_flags & FL_POSIX) == 0)
                 return 1;
 
-        mutex_lock(&cinode->lock_mutex);
+        down_read(&cinode->lock_sem);
         posix_test_lock(file, flock);
 
         if (flock->fl_type == F_UNLCK && !cinode->can_cache_brlcks) {
@@ -864,7 +864,7 @@ cifs_posix_lock_test(struct file *file, struct file_lock *flock)
                 rc = 1;
         }
 
-        mutex_unlock(&cinode->lock_mutex);
+        up_read(&cinode->lock_sem);
         return rc;
 }
 
@@ -884,14 +884,14 @@ cifs_posix_lock_set(struct file *file, struct file_lock *flock)
                 return rc;
 
 try_again:
-        mutex_lock(&cinode->lock_mutex);
+        down_write(&cinode->lock_sem);
         if (!cinode->can_cache_brlcks) {
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 return rc;
         }
 
         rc = posix_lock_file(file, flock, NULL);
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
         if (rc == FILE_LOCK_DEFERRED) {
                 rc = wait_event_interruptible(flock->fl_wait, !flock->fl_next);
                 if (!rc)
@@ -918,9 +918,10 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
         xid = get_xid();
         tcon = tlink_tcon(cfile->tlink);
 
-        mutex_lock(&cinode->lock_mutex);
+        /* we are going to update can_cache_brlcks here - need a write access */
+        down_write(&cinode->lock_sem);
         if (!cinode->can_cache_brlcks) {
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 free_xid(xid);
                 return rc;
         }
@@ -931,7 +932,7 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
          */
         max_buf = tcon->ses->server->maxBuf;
         if (!max_buf) {
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 free_xid(xid);
                 return -EINVAL;
         }
@@ -940,7 +941,7 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
                                                 sizeof(LOCKING_ANDX_RANGE);
         buf = kzalloc(max_num * sizeof(LOCKING_ANDX_RANGE), GFP_KERNEL);
         if (!buf) {
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 free_xid(xid);
                 return -ENOMEM;
         }
@@ -978,7 +979,7 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
         }
 
         cinode->can_cache_brlcks = false;
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
 
         kfree(buf);
         free_xid(xid);
@@ -1013,9 +1014,10 @@ cifs_push_posix_locks(struct cifsFileInfo *cfile)
 
         xid = get_xid();
 
-        mutex_lock(&cinode->lock_mutex);
+        /* we are going to update can_cache_brlcks here - need a write access */
+        down_write(&cinode->lock_sem);
         if (!cinode->can_cache_brlcks) {
-                mutex_unlock(&cinode->lock_mutex);
+                up_write(&cinode->lock_sem);
                 free_xid(xid);
                 return rc;
         }
@@ -1031,7 +1033,7 @@ cifs_push_posix_locks(struct cifsFileInfo *cfile)
 
         /*
          * Allocating count locks is enough because no FL_POSIX locks can be
-         * added to the list while we are holding cinode->lock_mutex that
+         * added to the list while we are holding cinode->lock_sem that
          * protects locking operations of this inode.
          */
         for (; i < count; i++) {
@@ -1086,7 +1088,7 @@ cifs_push_posix_locks(struct cifsFileInfo *cfile)
 
 out:
         cinode->can_cache_brlcks = false;
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
 
         free_xid(xid);
         return rc;
@@ -1278,7 +1280,7 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
         if (!buf)
                 return -ENOMEM;
 
-        mutex_lock(&cinode->lock_mutex);
+        down_write(&cinode->lock_sem);
         for (i = 0; i < 2; i++) {
                 cur = buf;
                 num = 0;
@@ -1348,7 +1350,7 @@ cifs_unlock_range(struct cifsFileInfo *cfile, struct file_lock *flock,
                 }
         }
 
-        mutex_unlock(&cinode->lock_mutex);
+        up_write(&cinode->lock_sem);
         kfree(buf);
         return rc;
 }