* Author: Phil Schwan <phil@clusterfs.com>
*/
+/**
+ * This file contains implementation of IBITS lock type
+ *
+ * IBITS lock type contains a bit mask determining various properties of an
+ * object. The meanings of specific bits are specific to the caller and are
+ * opaque to LDLM code.
+ *
+ * Locks with intersecting bitmasks and conflicting lock modes (e.g. LCK_PW)
+ * are considered conflicting. See the lock mode compatibility matrix
+ * in lustre_dlm.h.
+ */
+
#define DEBUG_SUBSYSTEM S_LDLM
#ifndef __KERNEL__
# include <liblustre.h>
#include "ldlm_internal.h"
#ifdef HAVE_SERVER_SUPPORT
-/* Determine if the lock is compatible with all locks on the queue. */
+/**
+ * Determine if the lock is compatible with all locks on the queue.
+ *
+ * If \a work_list is provided, conflicting locks are linked there.
+ * If \a work_list is not provided, we exit this function on first conflict.
+ *
+ * \retval 0 if there are conflicting locks in the \a queue
+ * \retval 1 if the lock is compatible to all locks in \a queue
+ *
+ * IBITS locks in granted queue are organized in bunches of
+ * same-mode/same-bits locks called "skip lists". The First lock in the
+ * bunch contains a pointer to the end of the bunch. This allows us to
+ * skip an entire bunch when iterating the list in search for conflicting
+ * locks if first lock of the bunch is not conflicting with us.
+ */
static int
ldlm_inodebits_compat_queue(cfs_list_t *queue, struct ldlm_lock *req,
cfs_list_t *work_list)
lock = cfs_list_entry(tmp, struct ldlm_lock, l_res_link);
+ /* We stop walking the queue if we hit ourselves so we don't
+ * take conflicting locks enqueued after us into account,
+ * or we'd wait forever. */
if (req == lock)
RETURN(compat);
for (;;) {
cfs_list_t *head;
- /* last lock in policy group */
- tmp = &cfs_list_entry(lock->l_sl_policy.prev,
- struct ldlm_lock,
- l_sl_policy)->l_res_link;
-
- /* locks with bits overlapped are conflicting locks */
- if (lock->l_policy_data.l_inodebits.bits & req_bits) {
- /* COS lock from the same client is
- not conflicting */
- if (lock->l_req_mode == LCK_COS &&
- lock->l_client_cookie == req->l_client_cookie)
- goto not_conflicting;
- /* conflicting policy */
- if (!work_list)
- RETURN(0);
-
- compat = 0;
-
- /* add locks of the policy group to
- * @work_list as blocking locks for
- * @req */
+ /* Advance loop cursor to last lock in policy group. */
+ tmp = &cfs_list_entry(lock->l_sl_policy.prev,
+ struct ldlm_lock,
+ l_sl_policy)->l_res_link;
+
+ /* Locks with overlapping bits conflict. */
+ if (lock->l_policy_data.l_inodebits.bits & req_bits) {
+ /* COS lock mode has a special compatibility
+ * requirement: it is only compatible with
+ * locks from the same client. */
+ if (lock->l_req_mode == LCK_COS &&
+ lock->l_client_cookie == req->l_client_cookie)
+ goto not_conflicting;
+ /* Found a conflicting policy group. */
+ if (!work_list)
+ RETURN(0);
+
+ compat = 0;
+
+ /* Add locks of the policy group to @work_list
+ * as blocking locks for @req */
if (lock->l_blocking_ast)
ldlm_add_ast_work_item(lock, req,
work_list);
tmp = tmp->next;
lock = cfs_list_entry(tmp, struct ldlm_lock,
l_res_link);
- } /* loop over policy groups within one mode group */
- } /* loop over mode groups within @queue */
+ } /* Loop over policy groups within one mode group. */
+ } /* Loop over mode groups within @queue. */
- RETURN(compat);
+ RETURN(compat);
}
-/* If first_enq is 0 (ie, called from ldlm_reprocess_queue):
- * - blocking ASTs have already been sent
- * - must call this function with the ns lock held
- *
- * If first_enq is 1 (ie, called from ldlm_lock_enqueue):
- * - blocking ASTs have not been sent
- * - must call this function with the ns lock held once */
+/**
+ * Process a granting attempt for IBITS lock.
+ * Must be called with ns lock held
+ *
+ * This function looks for any conflicts for \a lock in the granted or
+ * waiting queues. The lock is granted if no conflicts are found in
+ * either queue.
+ *
+ * If \a first_enq is 0 (ie, called from ldlm_reprocess_queue):
+ * - blocking ASTs have already been sent
+ *
+ * If \a first_enq is 1 (ie, called from ldlm_lock_enqueue):
+ * - blocking ASTs have not been sent yet, so list of conflicting locks
+ * would be collected and ASTs sent.
+ */
int ldlm_process_inodebits_lock(struct ldlm_lock *lock, __u64 *flags,
int first_enq, ldlm_error_t *err,
cfs_list_t *work_list)
git://git.whamcloud.com / fs / lustre-release.git / blobdiff