diff options
author | Dmitry Torokhov <dtor@insightbb.com> | 2007-02-10 01:26:32 -0500 |
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committer | Dmitry Torokhov <dtor@insightbb.com> | 2007-02-10 01:26:32 -0500 |
commit | b22364c8eec89e6b0c081a237f3b6348df87796f (patch) | |
tree | 233a923281fb640106465d076997ff511efb6edf /fs/direct-io.c | |
parent | 2c8dc071517ec2843869024dc82be2e246f41064 (diff) | |
parent | 66efc5a7e3061c3597ac43a8bb1026488d57e66b (diff) |
Merge rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6
Diffstat (limited to 'fs/direct-io.c')
-rw-r--r-- | fs/direct-io.c | 323 |
1 files changed, 144 insertions, 179 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c index 5981e17f46f..d9d0833444f 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -27,6 +27,7 @@ #include <linux/slab.h> #include <linux/highmem.h> #include <linux/pagemap.h> +#include <linux/task_io_accounting_ops.h> #include <linux/bio.h> #include <linux/wait.h> #include <linux/err.h> @@ -121,8 +122,7 @@ struct dio { /* BIO completion state */ spinlock_t bio_lock; /* protects BIO fields below */ - int bio_count; /* nr bios to be completed */ - int bios_in_flight; /* nr bios in flight */ + 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) */ @@ -209,76 +209,55 @@ static struct page *dio_get_page(struct dio *dio) return dio->pages[dio->head++]; } -/* - * Called when all DIO BIO I/O has been completed - let the filesystem - * know, if it registered an interest earlier via get_block. Pass the - * private field of the map buffer_head so that filesystems can use it - * to hold additional state between get_block calls and dio_complete. - */ -static void dio_complete(struct dio *dio, loff_t offset, ssize_t bytes) -{ - if (dio->end_io && dio->result) - dio->end_io(dio->iocb, offset, bytes, dio->map_bh.b_private); - if (dio->lock_type == DIO_LOCKING) - /* lockdep: non-owner release */ - up_read_non_owner(&dio->inode->i_alloc_sem); -} - -/* - * Called when a BIO has been processed. If the count goes to zero then IO is - * complete and we can signal this to the AIO layer. +/** + * dio_complete() - called when all DIO BIO I/O has been completed + * @offset: the byte offset in the file of the completed operation + * + * This releases locks as dictated by the locking type, lets interested parties + * know that a DIO operation has completed, and calculates the resulting return + * code for the operation. + * + * It lets the filesystem know if it registered an interest earlier via + * get_block. Pass the private field of the map buffer_head so that + * filesystems can use it to hold additional state between get_block calls and + * dio_complete. */ -static void finished_one_bio(struct dio *dio) +static int dio_complete(struct dio *dio, loff_t offset, int ret) { - unsigned long flags; + ssize_t transferred = 0; - spin_lock_irqsave(&dio->bio_lock, flags); - if (dio->bio_count == 1) { - if (dio->is_async) { - ssize_t transferred; - loff_t offset; - - /* - * Last reference to the dio is going away. - * Drop spinlock and complete the DIO. - */ - spin_unlock_irqrestore(&dio->bio_lock, flags); + /* + * AIO submission can race with bio completion to get here while + * expecting to have the last io completed by bio completion. + * In that case -EIOCBQUEUED is in fact not an error we want + * to preserve through this call. + */ + if (ret == -EIOCBQUEUED) + ret = 0; - /* Check for short read case */ - transferred = dio->result; - offset = dio->iocb->ki_pos; + if (dio->result) { + transferred = dio->result; - if ((dio->rw == READ) && - ((offset + transferred) > dio->i_size)) - transferred = dio->i_size - offset; + /* Check for short read case */ + if ((dio->rw == READ) && ((offset + transferred) > dio->i_size)) + transferred = dio->i_size - offset; + } - /* check for error in completion path */ - if (dio->io_error) - transferred = dio->io_error; + if (dio->end_io && dio->result) + dio->end_io(dio->iocb, offset, transferred, + dio->map_bh.b_private); + if (dio->lock_type == DIO_LOCKING) + /* lockdep: non-owner release */ + up_read_non_owner(&dio->inode->i_alloc_sem); - dio_complete(dio, offset, transferred); + if (ret == 0) + ret = dio->page_errors; + if (ret == 0) + ret = dio->io_error; + if (ret == 0) + ret = transferred; - /* Complete AIO later if falling back to buffered i/o */ - if (dio->result == dio->size || - ((dio->rw == READ) && dio->result)) { - aio_complete(dio->iocb, transferred, 0); - kfree(dio); - return; - } else { - /* - * Falling back to buffered - */ - spin_lock_irqsave(&dio->bio_lock, flags); - dio->bio_count--; - if (dio->waiter) - wake_up_process(dio->waiter); - spin_unlock_irqrestore(&dio->bio_lock, flags); - return; - } - } - } - dio->bio_count--; - spin_unlock_irqrestore(&dio->bio_lock, flags); + return ret; } static int dio_bio_complete(struct dio *dio, struct bio *bio); @@ -288,12 +267,27 @@ 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; + unsigned long remaining; + unsigned long flags; if (bio->bi_size) return 1; /* cleanup the bio */ dio_bio_complete(dio, bio); + + 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); + aio_complete(dio->iocb, ret, 0); + kfree(dio); + } + return 0; } @@ -315,8 +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; - dio->bios_in_flight--; - if (dio->waiter && dio->bios_in_flight == 0) + if (--dio->refcount == 1 && dio->waiter) wake_up_process(dio->waiter); spin_unlock_irqrestore(&dio->bio_lock, flags); return 0; @@ -347,6 +340,8 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev, * In the AIO read case we speculatively dirty the pages before starting IO. * During IO completion, any of these pages which happen to have been written * back will be redirtied by bio_check_pages_dirty(). + * + * bios hold a dio reference between submit_bio and ->end_io. */ static void dio_bio_submit(struct dio *dio) { @@ -354,12 +349,14 @@ static void dio_bio_submit(struct dio *dio) unsigned long flags; bio->bi_private = dio; + spin_lock_irqsave(&dio->bio_lock, flags); - dio->bio_count++; - dio->bios_in_flight++; + 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; @@ -376,28 +373,37 @@ static void dio_cleanup(struct dio *dio) } /* - * Wait for the next BIO to complete. Remove it and return it. + * 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 + * all bios have been issued so that dio->refcount can only decrease. This + * requires that that the caller hold a reference on the dio. */ static struct bio *dio_await_one(struct dio *dio) { unsigned long flags; - struct bio *bio; + struct bio *bio = NULL; spin_lock_irqsave(&dio->bio_lock, flags); - while (dio->bio_list == NULL) { - set_current_state(TASK_UNINTERRUPTIBLE); - if (dio->bio_list == NULL) { - dio->waiter = current; - spin_unlock_irqrestore(&dio->bio_lock, flags); - blk_run_address_space(dio->inode->i_mapping); - 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; + dio->bio_list = bio->bi_private; } - bio = dio->bio_list; - dio->bio_list = bio->bi_private; spin_unlock_irqrestore(&dio->bio_lock, flags); return bio; } @@ -426,34 +432,24 @@ static int dio_bio_complete(struct dio *dio, struct bio *bio) } bio_put(bio); } - finished_one_bio(dio); return uptodate ? 0 : -EIO; } /* - * Wait on and process all in-flight BIOs. + * Wait on and process all in-flight BIOs. This must only be called once + * all bios have been issued so that the refcount can only decrease. + * This just waits for all bios to make it through dio_bio_complete. IO + * errors are propogated through dio->io_error and should be propogated via + * dio_complete(). */ -static int dio_await_completion(struct dio *dio) +static void dio_await_completion(struct dio *dio) { - int ret = 0; - - if (dio->bio) - dio_bio_submit(dio); - - /* - * The bio_lock is not held for the read of bio_count. - * This is ok since it is the dio_bio_complete() that changes - * bio_count. - */ - while (dio->bio_count) { - struct bio *bio = dio_await_one(dio); - int ret2; - - ret2 = dio_bio_complete(dio, bio); - if (ret == 0) - ret = ret2; - } - return ret; + struct bio *bio; + do { + bio = dio_await_one(dio); + if (bio) + dio_bio_complete(dio, bio); + } while (bio); } /* @@ -675,6 +671,13 @@ submit_page_section(struct dio *dio, struct page *page, { int ret = 0; + if (dio->rw & WRITE) { + /* + * Read accounting is performed in submit_bio() + */ + task_io_account_write(len); + } + /* * Can we just grow the current page's presence in the dio? */ @@ -953,6 +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; @@ -983,17 +987,8 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, dio->iocb = iocb; dio->i_size = i_size_read(inode); - /* - * BIO completion state. - * - * ->bio_count starts out at one, and we decrement it to zero after all - * BIOs are submitted. This to avoid the situation where a really fast - * (or synchronous) device could take the count to zero while we're - * still submitting BIOs. - */ - dio->bio_count = 1; - dio->bios_in_flight = 0; spin_lock_init(&dio->bio_lock); + dio->refcount = 1; dio->bio_list = NULL; dio->waiter = NULL; @@ -1069,6 +1064,9 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, if (dio->bio) dio_bio_submit(dio); + /* All IO is now issued, send it on its way */ + blk_run_address_space(inode->i_mapping); + /* * It is possible that, we return short IO due to end of file. * In that case, we need to release all the pages we got hold on. @@ -1084,74 +1082,41 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, mutex_unlock(&dio->inode->i_mutex); /* - * OK, all BIOs are submitted, so we can decrement bio_count to truly - * reflect the number of to-be-processed BIOs. + * The only time we want to leave bios in flight is when a successful + * partial aio read or full aio write have been setup. In that case + * bio completion will call aio_complete. The only time it's safe to + * call aio_complete is when we return -EIOCBQUEUED, so we key on that. + * This had *better* be the only place that raises -EIOCBQUEUED. */ - if (dio->is_async) { - int should_wait = 0; + BUG_ON(ret == -EIOCBQUEUED); + if (dio->is_async && ret == 0 && dio->result && + ((rw & READ) || (dio->result == dio->size))) + ret = -EIOCBQUEUED; - if (dio->result < dio->size && (rw & WRITE)) { - dio->waiter = current; - should_wait = 1; - } - if (ret == 0) - ret = dio->result; - finished_one_bio(dio); /* This can free the dio */ - blk_run_address_space(inode->i_mapping); - if (should_wait) { - unsigned long flags; - /* - * Wait for already issued I/O to drain out and - * release its references to user-space pages - * before returning to fallback on buffered I/O - */ - - spin_lock_irqsave(&dio->bio_lock, flags); - set_current_state(TASK_UNINTERRUPTIBLE); - while (dio->bio_count) { - spin_unlock_irqrestore(&dio->bio_lock, flags); - io_schedule(); - spin_lock_irqsave(&dio->bio_lock, flags); - set_current_state(TASK_UNINTERRUPTIBLE); - } - spin_unlock_irqrestore(&dio->bio_lock, flags); - set_current_state(TASK_RUNNING); - kfree(dio); - } - } else { - ssize_t transferred = 0; - - finished_one_bio(dio); - ret2 = dio_await_completion(dio); - if (ret == 0) - ret = ret2; - if (ret == 0) - ret = dio->page_errors; - if (dio->result) { - loff_t i_size = i_size_read(inode); - - transferred = dio->result; - /* - * Adjust the return value if the read crossed a - * non-block-aligned EOF. - */ - if (rw == READ && (offset + transferred > i_size)) - transferred = i_size - offset; - } - dio_complete(dio, offset, transferred); - if (ret == 0) - ret = transferred; + if (ret != -EIOCBQUEUED) + dio_await_completion(dio); - /* We could have also come here on an AIO file extend */ - if (!is_sync_kiocb(iocb) && (rw & WRITE) && - ret >= 0 && dio->result == dio->size) - /* - * For AIO writes where we have completed the - * i/o, we have to mark the the aio complete. - */ - aio_complete(iocb, ret, 0); + /* + * 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(). + * + * 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. + */ + 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 + BUG_ON(ret != -EIOCBQUEUED); + return ret; } |