| Message ID | 1425306313-7234-5-git-send-email-daniel.wagner@bmw-carit.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon, 2 Mar 2015 15:25:13 +0100 Daniel Wagner <daniel.wagner@bmw-carit.de> wrote: > blocked_lock_lock and file_lock_lglock is used to protect file_lock's > fl_link, fl_block, fl_next, blocked_hash and the percpu > file_lock_list. > > The plan is to reorganize the usage of the locks and what they protect > so that the usage of the global blocked_lock_lock is reduced. > > Whenever we insert a new lock we are going to grab besides the > flc_lock also the corresponding file_lock_lglock. The global > blocked_lock_lock is only used when blocked_hash is involved. > > file_lock_lglock protects now file_lock_list and fl_link, fl_block and > fl_next allone. That means we need to define which file_lock_lglock is > used for all waiters. Luckely, fl_link_cpu can be reused for fl_block > and fl_next. > > Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de> > Cc: Jeff Layton <jlayton@poochiereds.net> > Cc: "J. Bruce Fields" <bfields@fieldses.org> > Cc: Alexander Viro <viro@zeniv.linux.org.uk> > --- > fs/locks.c | 78 ++++++++++++++++++++++++++++++++++---------------------------- > 1 file changed, 43 insertions(+), 35 deletions(-) > > diff --git a/fs/locks.c b/fs/locks.c > index 02821dd..de15ea8 100644 > --- a/fs/locks.c > +++ b/fs/locks.c > @@ -162,6 +162,20 @@ int lease_break_time = 45; > * keep a list on each CPU, with each list protected by its own spinlock via > * the file_lock_lglock. Note that alterations to the list also require that > * the relevant flc_lock is held. > + * > + * In addition, it also protects the fl->fl_block list, and the fl->fl_next > + * pointer for file_lock structures that are acting as lock requests (in > + * contrast to those that are acting as records of acquired locks). > + * > + * file_lock structures acting as lock requests (waiters) use the same > + * spinlock as the those acting as lock holder (blocker). E.g. the > + * blocker is initially added to the file_lock_list living on CPU 0, > + * all waiters on that blocker are serialized via CPU 0 (see > + * fl_link_cpu usage). > + * > + * In particular, adding an entry to the fl_block list requires that you hold > + * both the flc_lock and the blocked_lock_lock (acquired in that order). > + * Deleting an entry from the list however only requires the file_lock_gllock. > */ > DEFINE_STATIC_LGLOCK(file_lock_lglock); > static DEFINE_PER_CPU(struct hlist_head, file_lock_list); > @@ -183,19 +197,6 @@ static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS); > /* > * This lock protects the blocked_hash. Generally, if you're accessing it, you > * want to be holding this lock. > - * > - * In addition, it also protects the fl->fl_block list, and the fl->fl_next > - * pointer for file_lock structures that are acting as lock requests (in > - * contrast to those that are acting as records of acquired locks). > - * > - * Note that when we acquire this lock in order to change the above fields, > - * we often hold the flc_lock as well. In certain cases, when reading the fields > - * protected by this lock, we can skip acquiring it iff we already hold the > - * flc_lock. > - * > - * In particular, adding an entry to the fl_block list requires that you hold > - * both the flc_lock and the blocked_lock_lock (acquired in that order). > - * Deleting an entry from the list however only requires the file_lock_lock. > */ > static DEFINE_SPINLOCK(blocked_lock_lock); > > @@ -607,7 +608,7 @@ static void locks_delete_global_blocked(struct file_lock *waiter) > /* Remove waiter from blocker's block list. > * When blocker ends up pointing to itself then the list is empty. > * > - * Must be called with blocked_lock_lock held. > + * Must be called with file_lock_lglock held. > */ > static void __locks_delete_block(struct file_lock *waiter) > { > @@ -617,7 +618,7 @@ static void __locks_delete_block(struct file_lock *waiter) > > /* Posix block variant of __locks_delete_block. > * > - * Must be called with blocked_lock_lock held. > + * Must be called with file_lock_lglock held. > */ > static void __locks_delete_posix_block(struct file_lock *waiter) > { > @@ -627,16 +628,18 @@ static void __locks_delete_posix_block(struct file_lock *waiter) > > static void locks_delete_block(struct file_lock *waiter) > { > - spin_lock(&blocked_lock_lock); > + lg_local_lock_cpu(&file_lock_lglock, waiter->fl_link_cpu); > __locks_delete_block(waiter); > - spin_unlock(&blocked_lock_lock); > + lg_local_unlock_cpu(&file_lock_lglock, waiter->fl_link_cpu); > } > > static void locks_delete_posix_block(struct file_lock *waiter) > { > + lg_local_lock_cpu(&file_lock_lglock, waiter->fl_link_cpu); > spin_lock(&blocked_lock_lock); > __locks_delete_posix_block(waiter); > spin_unlock(&blocked_lock_lock); > + lg_local_unlock_cpu(&file_lock_lglock, waiter->fl_link_cpu); > } > > /* Insert waiter into blocker's block list. > @@ -644,22 +647,23 @@ static void locks_delete_posix_block(struct file_lock *waiter) > * the order they blocked. The documentation doesn't require this but > * it seems like the reasonable thing to do. > * > - * Must be called with both the flc_lock and blocked_lock_lock held. The > - * fl_block list itself is protected by the blocked_lock_lock, but by ensuring > + * Must be called with both the flc_lock and file_lock_lglock held. The > + * fl_block list itself is protected by the file_lock_lglock, but by ensuring > * that the flc_lock is also held on insertions we can avoid taking the > - * blocked_lock_lock in some cases when we see that the fl_block list is empty. > + * file_lock_lglock in some cases when we see that the fl_block list is empty. > */ > static void __locks_insert_block(struct file_lock *blocker, > struct file_lock *waiter) > { > BUG_ON(!list_empty(&waiter->fl_block)); > + waiter->fl_link_cpu = blocker->fl_link_cpu; > waiter->fl_next = blocker; > list_add_tail(&waiter->fl_block, &blocker->fl_block); > } > > /* Posix block variant of __locks_insert_block. > * > - * Must be called with flc_lock and blocked_lock_lock held. > + * Must be called with flc_lock and file_lock_lglock held. > */ > static void __locks_insert_posix_block(struct file_lock *blocker, > struct file_lock *waiter) > @@ -673,9 +677,9 @@ static void __locks_insert_posix_block(struct file_lock *blocker, > static void locks_insert_block(struct file_lock *blocker, > struct file_lock *waiter) > { > - spin_lock(&blocked_lock_lock); > + lg_local_lock_cpu(&file_lock_lglock, blocker->fl_link_cpu); > __locks_insert_block(blocker, waiter); > - spin_unlock(&blocked_lock_lock); > + lg_local_unlock_cpu(&file_lock_lglock, blocker->fl_link_cpu); > } > > /* > @@ -686,31 +690,33 @@ static void locks_insert_block(struct file_lock *blocker, > static void locks_wake_up_blocks(struct file_lock *blocker) > { > /* > - * Avoid taking global lock if list is empty. This is safe since new > + * Avoid taking lock if list is empty. This is safe since new > * blocked requests are only added to the list under the flc_lock, and > * the flc_lock is always held here. Note that removal from the fl_block > * list does not require the flc_lock, so we must recheck list_empty() > - * after acquiring the blocked_lock_lock. > + * after acquiring the file_lock_lglock. > */ > if (list_empty(&blocker->fl_block)) > return; > > - spin_lock(&blocked_lock_lock); > + lg_local_lock_cpu(&file_lock_lglock, blocker->fl_link_cpu); > while (!list_empty(&blocker->fl_block)) { > struct file_lock *waiter; > > waiter = list_first_entry(&blocker->fl_block, > struct file_lock, fl_block); > - if (IS_POSIX(blocker)) > + if (IS_POSIX(blocker)) { > + spin_lock(&blocked_lock_lock); > __locks_delete_posix_block(waiter); > - else > + spin_unlock(&blocked_lock_lock); > + } else > __locks_delete_block(waiter); So again, as I tried to point out in the last patch, I think we can do better here and also avoid taking the blocked_lock_lock when the blocker is an OFD lock. > if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) > waiter->fl_lmops->lm_notify(waiter); > else > wake_up(&waiter->fl_wait); > } > - spin_unlock(&blocked_lock_lock); > + lg_local_unlock_cpu(&file_lock_lglock, blocker->fl_link_cpu); > } > > static void > @@ -737,9 +743,11 @@ static void > locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose) > { > locks_unlink_lock_ctx(fl); > - if (dispose) > + if (dispose) { > + lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu); > list_add(&fl->fl_list, dispose); > - else > + lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu); > + } else > locks_free_lock(fl); > } > > @@ -1011,12 +1019,14 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str > * locks list must be done while holding the same lock! > */ > error = -EDEADLK; > + lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu); > spin_lock(&blocked_lock_lock); > if (likely(!posix_locks_deadlock(request, fl))) { > error = FILE_LOCK_DEFERRED; > __locks_insert_posix_block(fl, request); > } > spin_unlock(&blocked_lock_lock); > + lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu); > goto out; > } > } > @@ -2497,12 +2507,14 @@ posix_unblock_lock(struct file_lock *waiter) > { > int status = 0; > > + lg_local_lock_cpu(&file_lock_lglock, waiter->fl_link_cpu); > spin_lock(&blocked_lock_lock); > if (waiter->fl_next) > __locks_delete_posix_block(waiter); > else > status = -ENOENT; > spin_unlock(&blocked_lock_lock); > + lg_local_unlock_cpu(&file_lock_lglock, waiter->fl_link_cpu); > return status; > } > EXPORT_SYMBOL(posix_unblock_lock); > @@ -2629,13 +2641,11 @@ static int locks_show(struct seq_file *f, void *v) > } > > static void *locks_start(struct seq_file *f, loff_t *pos) > - __acquires(&blocked_lock_lock) > { > struct locks_iterator *iter = f->private; > > iter->li_pos = *pos + 1; > lg_global_lock(&file_lock_lglock); > - spin_lock(&blocked_lock_lock); > return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos); > } > > @@ -2648,9 +2658,7 @@ static void *locks_next(struct seq_file *f, void *v, loff_t *pos) > } > > static void locks_stop(struct seq_file *f, void *v) > - __releases(&blocked_lock_lock) > { > - spin_unlock(&blocked_lock_lock); > lg_global_unlock(&file_lock_lglock); > } >
diff --git a/fs/locks.c b/fs/locks.c index 02821dd..de15ea8 100644 --- a/fs/locks.c +++ b/fs/locks.c @@ -162,6 +162,20 @@ int lease_break_time = 45; * keep a list on each CPU, with each list protected by its own spinlock via * the file_lock_lglock. Note that alterations to the list also require that * the relevant flc_lock is held. + * + * In addition, it also protects the fl->fl_block list, and the fl->fl_next + * pointer for file_lock structures that are acting as lock requests (in + * contrast to those that are acting as records of acquired locks). + * + * file_lock structures acting as lock requests (waiters) use the same + * spinlock as the those acting as lock holder (blocker). E.g. the + * blocker is initially added to the file_lock_list living on CPU 0, + * all waiters on that blocker are serialized via CPU 0 (see + * fl_link_cpu usage). + * + * In particular, adding an entry to the fl_block list requires that you hold + * both the flc_lock and the blocked_lock_lock (acquired in that order). + * Deleting an entry from the list however only requires the file_lock_gllock. */ DEFINE_STATIC_LGLOCK(file_lock_lglock); static DEFINE_PER_CPU(struct hlist_head, file_lock_list); @@ -183,19 +197,6 @@ static DEFINE_HASHTABLE(blocked_hash, BLOCKED_HASH_BITS); /* * This lock protects the blocked_hash. Generally, if you're accessing it, you * want to be holding this lock. - * - * In addition, it also protects the fl->fl_block list, and the fl->fl_next - * pointer for file_lock structures that are acting as lock requests (in - * contrast to those that are acting as records of acquired locks). - * - * Note that when we acquire this lock in order to change the above fields, - * we often hold the flc_lock as well. In certain cases, when reading the fields - * protected by this lock, we can skip acquiring it iff we already hold the - * flc_lock. - * - * In particular, adding an entry to the fl_block list requires that you hold - * both the flc_lock and the blocked_lock_lock (acquired in that order). - * Deleting an entry from the list however only requires the file_lock_lock. */ static DEFINE_SPINLOCK(blocked_lock_lock); @@ -607,7 +608,7 @@ static void locks_delete_global_blocked(struct file_lock *waiter) /* Remove waiter from blocker's block list. * When blocker ends up pointing to itself then the list is empty. * - * Must be called with blocked_lock_lock held. + * Must be called with file_lock_lglock held. */ static void __locks_delete_block(struct file_lock *waiter) { @@ -617,7 +618,7 @@ static void __locks_delete_block(struct file_lock *waiter) /* Posix block variant of __locks_delete_block. * - * Must be called with blocked_lock_lock held. + * Must be called with file_lock_lglock held. */ static void __locks_delete_posix_block(struct file_lock *waiter) { @@ -627,16 +628,18 @@ static void __locks_delete_posix_block(struct file_lock *waiter) static void locks_delete_block(struct file_lock *waiter) { - spin_lock(&blocked_lock_lock); + lg_local_lock_cpu(&file_lock_lglock, waiter->fl_link_cpu); __locks_delete_block(waiter); - spin_unlock(&blocked_lock_lock); + lg_local_unlock_cpu(&file_lock_lglock, waiter->fl_link_cpu); } static void locks_delete_posix_block(struct file_lock *waiter) { + lg_local_lock_cpu(&file_lock_lglock, waiter->fl_link_cpu); spin_lock(&blocked_lock_lock); __locks_delete_posix_block(waiter); spin_unlock(&blocked_lock_lock); + lg_local_unlock_cpu(&file_lock_lglock, waiter->fl_link_cpu); } /* Insert waiter into blocker's block list. @@ -644,22 +647,23 @@ static void locks_delete_posix_block(struct file_lock *waiter) * the order they blocked. The documentation doesn't require this but * it seems like the reasonable thing to do. * - * Must be called with both the flc_lock and blocked_lock_lock held. The - * fl_block list itself is protected by the blocked_lock_lock, but by ensuring + * Must be called with both the flc_lock and file_lock_lglock held. The + * fl_block list itself is protected by the file_lock_lglock, but by ensuring * that the flc_lock is also held on insertions we can avoid taking the - * blocked_lock_lock in some cases when we see that the fl_block list is empty. + * file_lock_lglock in some cases when we see that the fl_block list is empty. */ static void __locks_insert_block(struct file_lock *blocker, struct file_lock *waiter) { BUG_ON(!list_empty(&waiter->fl_block)); + waiter->fl_link_cpu = blocker->fl_link_cpu; waiter->fl_next = blocker; list_add_tail(&waiter->fl_block, &blocker->fl_block); } /* Posix block variant of __locks_insert_block. * - * Must be called with flc_lock and blocked_lock_lock held. + * Must be called with flc_lock and file_lock_lglock held. */ static void __locks_insert_posix_block(struct file_lock *blocker, struct file_lock *waiter) @@ -673,9 +677,9 @@ static void __locks_insert_posix_block(struct file_lock *blocker, static void locks_insert_block(struct file_lock *blocker, struct file_lock *waiter) { - spin_lock(&blocked_lock_lock); + lg_local_lock_cpu(&file_lock_lglock, blocker->fl_link_cpu); __locks_insert_block(blocker, waiter); - spin_unlock(&blocked_lock_lock); + lg_local_unlock_cpu(&file_lock_lglock, blocker->fl_link_cpu); } /* @@ -686,31 +690,33 @@ static void locks_insert_block(struct file_lock *blocker, static void locks_wake_up_blocks(struct file_lock *blocker) { /* - * Avoid taking global lock if list is empty. This is safe since new + * Avoid taking lock if list is empty. This is safe since new * blocked requests are only added to the list under the flc_lock, and * the flc_lock is always held here. Note that removal from the fl_block * list does not require the flc_lock, so we must recheck list_empty() - * after acquiring the blocked_lock_lock. + * after acquiring the file_lock_lglock. */ if (list_empty(&blocker->fl_block)) return; - spin_lock(&blocked_lock_lock); + lg_local_lock_cpu(&file_lock_lglock, blocker->fl_link_cpu); while (!list_empty(&blocker->fl_block)) { struct file_lock *waiter; waiter = list_first_entry(&blocker->fl_block, struct file_lock, fl_block); - if (IS_POSIX(blocker)) + if (IS_POSIX(blocker)) { + spin_lock(&blocked_lock_lock); __locks_delete_posix_block(waiter); - else + spin_unlock(&blocked_lock_lock); + } else __locks_delete_block(waiter); if (waiter->fl_lmops && waiter->fl_lmops->lm_notify) waiter->fl_lmops->lm_notify(waiter); else wake_up(&waiter->fl_wait); } - spin_unlock(&blocked_lock_lock); + lg_local_unlock_cpu(&file_lock_lglock, blocker->fl_link_cpu); } static void @@ -737,9 +743,11 @@ static void locks_delete_lock_ctx(struct file_lock *fl, struct list_head *dispose) { locks_unlink_lock_ctx(fl); - if (dispose) + if (dispose) { + lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu); list_add(&fl->fl_list, dispose); - else + lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu); + } else locks_free_lock(fl); } @@ -1011,12 +1019,14 @@ static int __posix_lock_file(struct inode *inode, struct file_lock *request, str * locks list must be done while holding the same lock! */ error = -EDEADLK; + lg_local_lock_cpu(&file_lock_lglock, fl->fl_link_cpu); spin_lock(&blocked_lock_lock); if (likely(!posix_locks_deadlock(request, fl))) { error = FILE_LOCK_DEFERRED; __locks_insert_posix_block(fl, request); } spin_unlock(&blocked_lock_lock); + lg_local_unlock_cpu(&file_lock_lglock, fl->fl_link_cpu); goto out; } } @@ -2497,12 +2507,14 @@ posix_unblock_lock(struct file_lock *waiter) { int status = 0; + lg_local_lock_cpu(&file_lock_lglock, waiter->fl_link_cpu); spin_lock(&blocked_lock_lock); if (waiter->fl_next) __locks_delete_posix_block(waiter); else status = -ENOENT; spin_unlock(&blocked_lock_lock); + lg_local_unlock_cpu(&file_lock_lglock, waiter->fl_link_cpu); return status; } EXPORT_SYMBOL(posix_unblock_lock); @@ -2629,13 +2641,11 @@ static int locks_show(struct seq_file *f, void *v) } static void *locks_start(struct seq_file *f, loff_t *pos) - __acquires(&blocked_lock_lock) { struct locks_iterator *iter = f->private; iter->li_pos = *pos + 1; lg_global_lock(&file_lock_lglock); - spin_lock(&blocked_lock_lock); return seq_hlist_start_percpu(&file_lock_list, &iter->li_cpu, *pos); } @@ -2648,9 +2658,7 @@ static void *locks_next(struct seq_file *f, void *v, loff_t *pos) } static void locks_stop(struct seq_file *f, void *v) - __releases(&blocked_lock_lock) { - spin_unlock(&blocked_lock_lock); lg_global_unlock(&file_lock_lglock); }
blocked_lock_lock and file_lock_lglock is used to protect file_lock's fl_link, fl_block, fl_next, blocked_hash and the percpu file_lock_list. The plan is to reorganize the usage of the locks and what they protect so that the usage of the global blocked_lock_lock is reduced. Whenever we insert a new lock we are going to grab besides the flc_lock also the corresponding file_lock_lglock. The global blocked_lock_lock is only used when blocked_hash is involved. file_lock_lglock protects now file_lock_list and fl_link, fl_block and fl_next allone. That means we need to define which file_lock_lglock is used for all waiters. Luckely, fl_link_cpu can be reused for fl_block and fl_next. Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de> Cc: Jeff Layton <jlayton@poochiereds.net> Cc: "J. Bruce Fields" <bfields@fieldses.org> Cc: Alexander Viro <viro@zeniv.linux.org.uk> --- fs/locks.c | 78 ++++++++++++++++++++++++++++++++++---------------------------- 1 file changed, 43 insertions(+), 35 deletions(-)