lockd: always preallocate block in nlmsvc_lock()

Normally we could skip ever having to allocate a block in the case where
the client asks for a non-blocking lock, or asks for a blocking lock that
succeeds immediately.

However we're going to want to always look up a block first in order to
check whether we're revisiting a deferred lock call, and to be prepared to
handle the case where the filesystem returns -EINPROGRESS--in that case we
want to make sure the lock we've given the filesystem is the one embedded
in the block that we'll use to track the deferred request.

Signed-off-by: Marc Eshel <eshel@almaden.ibm.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

1 files changed, 11 insertions, 23 deletions

diff --git a/fs/lockd/svclock.c b/fs/lockd/svclock.c
index b7a8174fd1dc..0d7398e3804f 100644
--- a/fs/lockd/svclock.c
+++ b/fs/lockd/svclock.c
@@ -365,7 +365,7 @@ __be32
 nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
                         struct nlm_lock *lock, int wait, struct nlm_cookie *cookie)
 {
-        struct nlm_block        *block, *newblock = NULL;
+        struct nlm_block        *block = NULL;
         int                     error;
         __be32                  ret;
 
@@ -378,17 +378,20 @@ nlmsvc_lock(struct svc_rqst *rqstp, struct nlm_file *file,
                                 wait);
 
 
-        lock->fl.fl_flags &= ~FL_SLEEP;
-again:
         /* Lock file against concurrent access */
         mutex_lock(&file->f_mutex);
-        /* Get existing block (in case client is busy-waiting) */
+        /* Get existing block (in case client is busy-waiting)
+         * or create new block
+         */
         block = nlmsvc_lookup_block(file, lock);
         if (block == NULL) {
-                if (newblock != NULL)
-                        lock = &newblock->b_call->a_args.lock;
-        } else
+                block = nlmsvc_create_block(rqstp, file, lock, cookie);
+                ret = nlm_lck_denied_nolocks;
+                if (block == NULL)
+                        goto out;
                 lock = &block->b_call->a_args.lock;
+        } else
+                lock->fl.fl_flags &= ~FL_SLEEP;
 
         error = posix_lock_file(file->f_file, &lock->fl, NULL);
         lock->fl.fl_flags &= ~FL_SLEEP;
@@ -414,26 +417,11 @@ again:
                 goto out;
 
         ret = nlm_lck_blocked;
-        if (block != NULL)
-                goto out;
-
-        /* If we don't have a block, create and initialize it. Then
-         * retry because we may have slept in kmalloc. */
-        /* We have to release f_mutex as nlmsvc_create_block may try to
-         * to claim it while doing host garbage collection */
-        if (newblock == NULL) {
-                mutex_unlock(&file->f_mutex);
-                dprintk("lockd: blocking on this lock (allocating).\n");
-                if (!(newblock = nlmsvc_create_block(rqstp, file, lock, cookie)))
-                        return nlm_lck_denied_nolocks;
-                goto again;
-        }
 
         /* Append to list of blocked */
-        nlmsvc_insert_block(newblock, NLM_NEVER);
+        nlmsvc_insert_block(block, NLM_NEVER);
 out:
         mutex_unlock(&file->f_mutex);
-        nlmsvc_release_block(newblock);
         nlmsvc_release_block(block);
         dprintk("lockd: nlmsvc_lock returned %u\n", ret);
         return ret;