From 7b7a8665edd8db733980389b098530f9e4f630b2 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 4 Sep 2013 15:04:39 +0200 Subject: direct-io: Implement generic deferred AIO completions Add support to the core direct-io code to defer AIO completions to user context using a workqueue. This replaces opencoded and less efficient code in XFS and ext4 (we save a memory allocation for each direct IO) and will be needed to properly support O_(D)SYNC for AIO. The communication between the filesystem and the direct I/O code requires a new buffer head flag, which is a bit ugly but not avoidable until the direct I/O code stops abusing the buffer_head structure for communicating with the filesystems. Currently this creates a per-superblock unbound workqueue for these completions, which is taken from an earlier patch by Jan Kara. I'm not really convinced about this use and would prefer a "normal" global workqueue with a high concurrency limit, but this needs further discussion. JK: Fixed ext4 part, dynamic allocation of the workqueue. Signed-off-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Al Viro --- fs/direct-io.c | 85 +++++++++++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 69 insertions(+), 16 deletions(-) (limited to 'fs/direct-io.c') diff --git a/fs/direct-io.c b/fs/direct-io.c index 7ab90f5081e..8b31b9f449f 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -127,6 +127,7 @@ struct dio { spinlock_t bio_lock; /* protects BIO fields below */ int page_errors; /* errno from get_user_pages() */ int is_async; /* is IO async ? */ + bool defer_completion; /* defer AIO completion to workqueue? */ int io_error; /* IO error in completion path */ unsigned long refcount; /* direct_io_worker() and bios */ struct bio *bio_list; /* singly linked via bi_private */ @@ -141,7 +142,10 @@ struct dio { * allocation time. Don't add new fields after pages[] unless you * wish that they not be zeroed. */ - struct page *pages[DIO_PAGES]; /* page buffer */ + union { + struct page *pages[DIO_PAGES]; /* page buffer */ + struct work_struct complete_work;/* deferred AIO completion */ + }; } ____cacheline_aligned_in_smp; static struct kmem_cache *dio_cache __read_mostly; @@ -221,16 +225,16 @@ static inline struct page *dio_get_page(struct dio *dio, * 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. + * This drops i_dio_count, 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 ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is_async) +static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, + bool is_async) { ssize_t transferred = 0; @@ -258,19 +262,26 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, bool is if (ret == 0) ret = transferred; - if (dio->end_io && dio->result) { - dio->end_io(dio->iocb, offset, transferred, - dio->private, ret, is_async); - } else { - inode_dio_done(dio->inode); - if (is_async) - aio_complete(dio->iocb, ret, 0); - } + if (dio->end_io && dio->result) + dio->end_io(dio->iocb, offset, transferred, dio->private); + + inode_dio_done(dio->inode); + if (is_async) + aio_complete(dio->iocb, ret, 0); + kmem_cache_free(dio_cache, dio); return ret; } +static void dio_aio_complete_work(struct work_struct *work) +{ + struct dio *dio = container_of(work, struct dio, complete_work); + + dio_complete(dio, dio->iocb->ki_pos, 0, true); +} + static int dio_bio_complete(struct dio *dio, struct bio *bio); + /* * Asynchronous IO callback. */ @@ -290,8 +301,13 @@ static void dio_bio_end_aio(struct bio *bio, int error) spin_unlock_irqrestore(&dio->bio_lock, flags); if (remaining == 0) { - dio_complete(dio, dio->iocb->ki_pos, 0, true); - kmem_cache_free(dio_cache, dio); + if (dio->result && dio->defer_completion) { + INIT_WORK(&dio->complete_work, dio_aio_complete_work); + queue_work(dio->inode->i_sb->s_dio_done_wq, + &dio->complete_work); + } else { + dio_complete(dio, dio->iocb->ki_pos, 0, true); + } } } @@ -510,6 +526,41 @@ static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) return ret; } +/* + * Create workqueue for deferred direct IO completions. We allocate the + * workqueue when it's first needed. This avoids creating workqueue for + * filesystems that don't need it and also allows us to create the workqueue + * late enough so the we can include s_id in the name of the workqueue. + */ +static int sb_init_dio_done_wq(struct super_block *sb) +{ + struct workqueue_struct *wq = alloc_workqueue("dio/%s", + WQ_MEM_RECLAIM, 0, + sb->s_id); + if (!wq) + return -ENOMEM; + /* + * This has to be atomic as more DIOs can race to create the workqueue + */ + cmpxchg(&sb->s_dio_done_wq, NULL, wq); + /* Someone created workqueue before us? Free ours... */ + if (wq != sb->s_dio_done_wq) + destroy_workqueue(wq); + return 0; +} + +static int dio_set_defer_completion(struct dio *dio) +{ + struct super_block *sb = dio->inode->i_sb; + + if (dio->defer_completion) + return 0; + dio->defer_completion = true; + if (!sb->s_dio_done_wq) + return sb_init_dio_done_wq(sb); + return 0; +} + /* * Call into the fs to map some more disk blocks. We record the current number * of available blocks at sdio->blocks_available. These are in units of the @@ -581,6 +632,9 @@ static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, /* Store for completion */ dio->private = map_bh->b_private; + + if (ret == 0 && buffer_defer_completion(map_bh)) + ret = dio_set_defer_completion(dio); } return ret; } @@ -1269,7 +1323,6 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, if (drop_refcount(dio) == 0) { retval = dio_complete(dio, offset, retval, false); - kmem_cache_free(dio_cache, dio); } else BUG_ON(retval != -EIOCBQUEUED); -- cgit v1.2.3-70-g09d2 From 02afc27faec94c9e068517a22acf55400976c698 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 4 Sep 2013 15:04:40 +0200 Subject: direct-io: Handle O_(D)SYNC AIO Call generic_write_sync() from the deferred I/O completion handler if O_DSYNC is set for a write request. Also make sure various callers don't call generic_write_sync if the direct I/O code returns -EIOCBQUEUED. Based on an earlier patch from Jan Kara with updates from Jeff Moyer and Darrick J. Wong . Signed-off-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Al Viro --- fs/block_dev.c | 2 +- fs/btrfs/file.c | 2 +- fs/cifs/file.c | 2 +- fs/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++--------- fs/ext4/file.c | 2 +- mm/filemap.c | 2 +- 6 files changed, 41 insertions(+), 14 deletions(-) (limited to 'fs/direct-io.c') diff --git a/fs/block_dev.c b/fs/block_dev.c index c7bda5cd3da..1173a4ee083 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1519,7 +1519,7 @@ ssize_t blkdev_aio_write(struct kiocb *iocb, const struct iovec *iov, blk_start_plug(&plug); ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); - if (ret > 0 || ret == -EIOCBQUEUED) { + if (ret > 0) { ssize_t err; err = generic_write_sync(file, pos, ret); diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 8e686a427ce..4d2eb641714 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1727,7 +1727,7 @@ static ssize_t btrfs_file_aio_write(struct kiocb *iocb, */ BTRFS_I(inode)->last_trans = root->fs_info->generation + 1; BTRFS_I(inode)->last_sub_trans = root->log_transid; - if (num_written > 0 || num_written == -EIOCBQUEUED) { + if (num_written > 0) { err = generic_write_sync(file, pos, num_written); if (err < 0 && num_written > 0) num_written = err; diff --git a/fs/cifs/file.c b/fs/cifs/file.c index 7e36ae34e94..9d0dd952ad7 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -2553,7 +2553,7 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov, mutex_unlock(&inode->i_mutex); } - if (rc > 0 || rc == -EIOCBQUEUED) { + if (rc > 0) { ssize_t err; err = generic_write_sync(file, pos, rc); diff --git a/fs/direct-io.c b/fs/direct-io.c index 8b31b9f449f..1782023bd68 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -266,8 +266,18 @@ static ssize_t dio_complete(struct dio *dio, loff_t offset, ssize_t ret, dio->end_io(dio->iocb, offset, transferred, dio->private); inode_dio_done(dio->inode); - if (is_async) + if (is_async) { + if (dio->rw & WRITE) { + int err; + + err = generic_write_sync(dio->iocb->ki_filp, offset, + transferred); + if (err < 0 && ret > 0) + ret = err; + } + aio_complete(dio->iocb, ret, 0); + } kmem_cache_free(dio_cache, dio); return ret; @@ -1182,11 +1192,6 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, } } - /* - * Will be decremented at I/O completion time. - */ - atomic_inc(&inode->i_dio_count); - /* * For file extending writes updating i_size before data * writeouts complete can expose uninitialized blocks. So @@ -1195,11 +1200,33 @@ do_blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, */ dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) && (end > i_size_read(inode))); - - retval = 0; - dio->inode = inode; dio->rw = rw; + + /* + * For AIO O_(D)SYNC writes we need to defer completions to a workqueue + * so that we can call ->fsync. + */ + if (dio->is_async && (rw & WRITE) && + ((iocb->ki_filp->f_flags & O_DSYNC) || + IS_SYNC(iocb->ki_filp->f_mapping->host))) { + retval = dio_set_defer_completion(dio); + if (retval) { + /* + * We grab i_mutex only for reads so we don't have + * to release it here + */ + kmem_cache_free(dio_cache, dio); + goto out; + } + } + + /* + * Will be decremented at I/O completion time. + */ + atomic_inc(&inode->i_dio_count); + + retval = 0; sdio.blkbits = blkbits; sdio.blkfactor = i_blkbits - blkbits; sdio.block_in_file = offset >> blkbits; diff --git a/fs/ext4/file.c b/fs/ext4/file.c index 319c9d26279..3da21945ff1 100644 --- a/fs/ext4/file.c +++ b/fs/ext4/file.c @@ -149,7 +149,7 @@ ext4_file_dio_write(struct kiocb *iocb, const struct iovec *iov, ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); mutex_unlock(&inode->i_mutex); - if (ret > 0 || ret == -EIOCBQUEUED) { + if (ret > 0) { ssize_t err; err = generic_write_sync(file, pos, ret); diff --git a/mm/filemap.c b/mm/filemap.c index 4b51ac1acae..731a2c24532 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2550,7 +2550,7 @@ ssize_t generic_file_aio_write(struct kiocb *iocb, const struct iovec *iov, ret = __generic_file_aio_write(iocb, iov, nr_segs, &iocb->ki_pos); mutex_unlock(&inode->i_mutex); - if (ret > 0 || ret == -EIOCBQUEUED) { + if (ret > 0) { ssize_t err; err = generic_write_sync(file, pos, ret); -- cgit v1.2.3-70-g09d2