diff options
Diffstat (limited to 'fs/direct-io.c')
| -rw-r--r-- | fs/direct-io.c | 76 |
1 files changed, 45 insertions, 31 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c index 71f4aeac7632..d9d0833444f5 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -121,8 +121,8 @@ struct dio { int page_errors; /* errno from get_user_pages() */ /* BIO completion state */ - atomic_t refcount; /* direct_io_worker() and bios */ spinlock_t bio_lock; /* protects BIO fields below */ + unsigned long refcount; /* direct_io_worker() and bios */ struct bio *bio_list; /* singly linked via bi_private */ struct task_struct *waiter; /* waiting task (NULL if none) */ @@ -267,8 +267,8 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio); static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) { struct dio *dio = bio->bi_private; - int waiter_holds_ref = 0; - int remaining; + unsigned long remaining; + unsigned long flags; if (bio->bi_size) return 1; @@ -276,10 +276,11 @@ static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) /* cleanup the bio */ dio_bio_complete(dio, bio); - waiter_holds_ref = !!dio->waiter; - remaining = atomic_sub_return(1, (&dio->refcount)); - if (remaining == 1 && waiter_holds_ref) + spin_lock_irqsave(&dio->bio_lock, flags); + remaining = --dio->refcount; + if (remaining == 1 && dio->waiter) wake_up_process(dio->waiter); + spin_unlock_irqrestore(&dio->bio_lock, flags); if (remaining == 0) { int ret = dio_complete(dio, dio->iocb->ki_pos, 0); @@ -308,7 +309,7 @@ static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error) spin_lock_irqsave(&dio->bio_lock, flags); bio->bi_private = dio->bio_list; dio->bio_list = bio; - if ((atomic_sub_return(1, &dio->refcount) == 1) && dio->waiter) + if (--dio->refcount == 1 && dio->waiter) wake_up_process(dio->waiter); spin_unlock_irqrestore(&dio->bio_lock, flags); return 0; @@ -345,11 +346,17 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev, static void dio_bio_submit(struct dio *dio) { struct bio *bio = dio->bio; + unsigned long flags; bio->bi_private = dio; - atomic_inc(&dio->refcount); + + spin_lock_irqsave(&dio->bio_lock, flags); + dio->refcount++; + spin_unlock_irqrestore(&dio->bio_lock, flags); + if (dio->is_async && dio->rw == READ) bio_set_pages_dirty(bio); + submit_bio(dio->rw, bio); dio->bio = NULL; @@ -365,13 +372,6 @@ static void dio_cleanup(struct dio *dio) page_cache_release(dio_get_page(dio)); } -static int wait_for_more_bios(struct dio *dio) -{ - assert_spin_locked(&dio->bio_lock); - - return (atomic_read(&dio->refcount) > 1) && (dio->bio_list == NULL); -} - /* * Wait for the next BIO to complete. Remove it and return it. NULL is * returned once all BIOs have been completed. This must only be called once @@ -384,16 +384,21 @@ static struct bio *dio_await_one(struct dio *dio) struct bio *bio = NULL; spin_lock_irqsave(&dio->bio_lock, flags); - while (wait_for_more_bios(dio)) { - set_current_state(TASK_UNINTERRUPTIBLE); - if (wait_for_more_bios(dio)) { - dio->waiter = current; - spin_unlock_irqrestore(&dio->bio_lock, flags); - io_schedule(); - spin_lock_irqsave(&dio->bio_lock, flags); - dio->waiter = NULL; - } - set_current_state(TASK_RUNNING); + + /* + * Wait as long as the list is empty and there are bios in flight. bio + * completion drops the count, maybe adds to the list, and wakes while + * holding the bio_lock so we don't need set_current_state()'s barrier + * and can call it after testing our condition. + */ + while (dio->refcount > 1 && dio->bio_list == NULL) { + __set_current_state(TASK_UNINTERRUPTIBLE); + dio->waiter = current; + spin_unlock_irqrestore(&dio->bio_lock, flags); + io_schedule(); + /* wake up sets us TASK_RUNNING */ + spin_lock_irqsave(&dio->bio_lock, flags); + dio->waiter = NULL; } if (dio->bio_list) { bio = dio->bio_list; @@ -951,6 +956,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, struct dio *dio) { unsigned long user_addr; + unsigned long flags; int seg; ssize_t ret = 0; ssize_t ret2; @@ -981,8 +987,8 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, dio->iocb = iocb; dio->i_size = i_size_read(inode); - atomic_set(&dio->refcount, 1); spin_lock_init(&dio->bio_lock); + dio->refcount = 1; dio->bio_list = NULL; dio->waiter = NULL; @@ -1092,12 +1098,20 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, /* * Sync will always be dropping the final ref and completing the - * operation. AIO can if it was a broken operation described above - * or in fact if all the bios race to complete before we get here. - * In that case dio_complete() translates the EIOCBQUEUED into - * the proper return code that the caller will hand to aio_complete(). + * operation. AIO can if it was a broken operation described above or + * in fact if all the bios race to complete before we get here. In + * that case dio_complete() translates the EIOCBQUEUED into the proper + * return code that the caller will hand to aio_complete(). + * + * This is managed by the bio_lock instead of being an atomic_t so that + * completion paths can drop their ref and use the remaining count to + * decide to wake the submission path atomically. */ - if (atomic_dec_and_test(&dio->refcount)) { + spin_lock_irqsave(&dio->bio_lock, flags); + ret2 = --dio->refcount; + spin_unlock_irqrestore(&dio->bio_lock, flags); + BUG_ON(!dio->is_async && ret2 != 0); + if (ret2 == 0) { ret = dio_complete(dio, offset, ret); kfree(dio); } else |