X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fdirect-io.c;h=7600aacf531dc8ed16ccfb727878d13834a16503;hb=75de46b98dda624397ccb17c106e51f478a79c15;hp=b05d1b218776946f4448ba2d0fd51cee477730cf;hpb=d4569d2e6949a63851032b40c811913d4a6f85f5;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/direct-io.c b/fs/direct-io.c index b05d1b2..7600aac 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -5,11 +5,11 @@ * * O_DIRECT * - * 04Jul2002 akpm@zip.com.au + * 04Jul2002 Andrew Morton * Initial version * 11Sep2002 janetinc@us.ibm.com * added readv/writev support. - * 29Oct2002 akpm@zip.com.au + * 29Oct2002 Andrew Morton * rewrote bio_add_page() support. * 30Oct2002 pbadari@us.ibm.com * added support for non-aligned IO. @@ -27,6 +27,7 @@ #include #include #include +#include #include #include #include @@ -52,13 +53,6 @@ * * If blkfactor is zero then the user's request was aligned to the filesystem's * blocksize. - * - * lock_type is DIO_LOCKING for regular files on direct-IO-naive filesystems. - * This determines whether we need to do the fancy locking which prevents - * direct-IO from being able to read uninitialised disk blocks. If its zero - * (blockdev) this locking is not done, and if it is DIO_OWN_LOCKING i_mutex is - * not held for the entire direct write (taken briefly, initially, during a - * direct read though, but its never held for the duration of a direct-IO). */ struct dio { @@ -67,7 +61,7 @@ struct dio { struct inode *inode; int rw; loff_t i_size; /* i_size when submitted */ - int lock_type; /* doesn't change */ + int flags; /* doesn't change */ unsigned blkbits; /* doesn't change */ unsigned blkfactor; /* When we're using an alignment which is finer than the filesystem's soft @@ -88,6 +82,8 @@ struct dio { int reap_counter; /* rate limit reaping */ get_block_t *get_block; /* block mapping function */ dio_iodone_t *end_io; /* IO completion function */ + dio_submit_t *submit_io; /* IO submition function */ + loff_t logical_offset_in_bio; /* current first logical block in bio */ sector_t final_block_in_bio; /* current final block in bio + 1 */ sector_t next_block_for_io; /* next block to be put under IO, in dio_blocks units */ @@ -102,6 +98,19 @@ struct dio { unsigned cur_page_offset; /* Offset into it, in bytes */ unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ sector_t cur_page_block; /* Where it starts */ + loff_t cur_page_fs_offset; /* Offset in file */ + + /* BIO completion state */ + 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) */ + + /* AIO related stuff */ + struct kiocb *iocb; /* kiocb */ + int is_async; /* is IO async ? */ + int io_error; /* IO error in completion path */ + ssize_t result; /* IO result */ /* * Page fetching state. These variables belong to dio_refill_pages(). @@ -114,23 +123,16 @@ struct dio { * Page queue. These variables belong to dio_refill_pages() and * dio_get_page(). */ - struct page *pages[DIO_PAGES]; /* page buffer */ unsigned head; /* next page to process */ unsigned tail; /* last valid page + 1 */ int page_errors; /* errno from get_user_pages() */ - /* 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 */ - struct bio *bio_list; /* singly linked via bi_private */ - struct task_struct *waiter; /* waiting task (NULL if none) */ - - /* AIO related stuff */ - struct kiocb *iocb; /* kiocb */ - int is_async; /* is IO async ? */ - int io_error; /* IO error in completion path */ - ssize_t result; /* IO result */ + /* + * pages[] (and any fields placed after it) are not zeroed out at + * allocation time. Don't add new fields after pages[] unless you + * wish that they not be zeroed. + */ + struct page *pages[DIO_PAGES]; /* page buffer */ }; /* @@ -150,20 +152,14 @@ static int dio_refill_pages(struct dio *dio) int nr_pages; nr_pages = min(dio->total_pages - dio->curr_page, DIO_PAGES); - down_read(¤t->mm->mmap_sem); - ret = get_user_pages( - current, /* Task for fault acounting */ - current->mm, /* whose pages? */ + ret = get_user_pages_fast( dio->curr_user_address, /* Where from? */ nr_pages, /* How many pages? */ dio->rw == READ, /* Write to memory? */ - 0, /* force (?) */ - &dio->pages[0], - NULL); /* vmas */ - up_read(¤t->mm->mmap_sem); + &dio->pages[0]); /* Put results here */ - if (ret < 0 && dio->blocks_available && (dio->rw == WRITE)) { - struct page *page = ZERO_PAGE(dio->curr_user_address); + if (ret < 0 && dio->blocks_available && (dio->rw & WRITE)) { + struct page *page = ZERO_PAGE(0); /* * A memory fault, but the filesystem has some outstanding * mapped blocks. We need to use those blocks up to avoid @@ -209,91 +205,82 @@ 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. +/** + * 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 dio_complete(struct dio *dio, loff_t offset, ssize_t bytes) +static int dio_complete(struct dio *dio, loff_t offset, int ret) { - if (dio->end_io && dio->result) - dio->end_io(dio->iocb, offset, bytes, dio->map_bh.b_private); - if (dio->lock_type == DIO_LOCKING) - up_read(&dio->inode->i_alloc_sem); -} + ssize_t transferred = 0; -/* - * 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. - */ -static void finished_one_bio(struct dio *dio) -{ - unsigned long 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; - spin_lock_irqsave(&dio->bio_lock, flags); - if (dio->bio_count == 1) { - if (dio->is_async) { - ssize_t transferred; - loff_t offset; + if (dio->result) { + transferred = dio->result; - /* - * Last reference to the dio is going away. - * Drop spinlock and complete the DIO. - */ - spin_unlock_irqrestore(&dio->bio_lock, flags); - - /* Check for short read case */ - transferred = dio->result; - offset = dio->iocb->ki_pos; + /* Check for short read case */ + if ((dio->rw == READ) && ((offset + transferred) > dio->i_size)) + transferred = dio->i_size - offset; + } - if ((dio->rw == READ) && - ((offset + transferred) > dio->i_size)) - transferred = dio->i_size - offset; + if (dio->end_io && dio->result) + dio->end_io(dio->iocb, offset, transferred, + dio->map_bh.b_private); - /* check for error in completion path */ - if (dio->io_error) - transferred = dio->io_error; + if (dio->flags & 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); /* * Asynchronous IO callback. */ -static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) +static void dio_bio_end_aio(struct bio *bio, int error) { struct dio *dio = bio->bi_private; - - if (bio->bi_size) - return 1; + unsigned long remaining; + unsigned long flags; /* cleanup the bio */ dio_bio_complete(dio, bio); - return 0; + + 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); + } } /* @@ -303,24 +290,39 @@ static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) * During I/O bi_private points at the dio. After I/O, bi_private is used to * implement a singly-linked list of completed BIOs, at dio->bio_list. */ -static int dio_bio_end_io(struct bio *bio, unsigned int bytes_done, int error) +static void dio_bio_end_io(struct bio *bio, int error) { struct dio *dio = bio->bi_private; unsigned long flags; - if (bio->bi_size) - return 1; - 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; } +/** + * dio_end_io - handle the end io action for the given bio + * @bio: The direct io bio thats being completed + * @error: Error if there was one + * + * This is meant to be called by any filesystem that uses their own dio_submit_t + * so that the DIO specific endio actions are dealt with after the filesystem + * has done it's completion work. + */ +void dio_end_io(struct bio *bio, int error) +{ + struct dio *dio = bio->bi_private; + + if (dio->is_async) + dio_bio_end_aio(bio, error); + else + dio_bio_end_io(bio, error); +} +EXPORT_SYMBOL_GPL(dio_end_io); + static int dio_bio_alloc(struct dio *dio, struct block_device *bdev, sector_t first_sector, int nr_vecs) @@ -328,8 +330,6 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev, struct bio *bio; bio = bio_alloc(GFP_KERNEL, nr_vecs); - if (bio == NULL) - return -ENOMEM; bio->bi_bdev = bdev; bio->bi_sector = first_sector; @@ -339,6 +339,7 @@ dio_bio_alloc(struct dio *dio, struct block_device *bdev, bio->bi_end_io = dio_bio_end_io; dio->bio = bio; + dio->logical_offset_in_bio = dio->cur_page_fs_offset; return 0; } @@ -346,6 +347,8 @@ 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) { @@ -353,16 +356,23 @@ 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); + + if (dio->submit_io) + dio->submit_io(dio->rw, bio, dio->inode, + dio->logical_offset_in_bio); + else + submit_bio(dio->rw, bio); dio->bio = NULL; dio->boundary = 0; + dio->logical_offset_in_bio = 0; } /* @@ -375,28 +385,37 @@ 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; } @@ -425,34 +444,24 @@ 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 propagated through dio->io_error and should be propagated 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); } /* @@ -535,21 +544,24 @@ static int get_more_blocks(struct dio *dio) map_bh->b_state = 0; map_bh->b_size = fs_count << dio->inode->i_blkbits; - create = dio->rw == WRITE; - if (dio->lock_type == DIO_LOCKING) { + /* + * For writes inside i_size on a DIO_SKIP_HOLES filesystem we + * forbid block creations: only overwrites are permitted. + * We will return early to the caller once we see an + * unmapped buffer head returned, and the caller will fall + * back to buffered I/O. + * + * Otherwise the decision is left to the get_blocks method, + * which may decide to handle it or also return an unmapped + * buffer head. + */ + create = dio->rw & WRITE; + if (dio->flags & DIO_SKIP_HOLES) { if (dio->block_in_file < (i_size_read(dio->inode) >> dio->blkbits)) create = 0; - } else if (dio->lock_type == DIO_NO_LOCKING) { - create = 0; } - /* - * For writes inside i_size we forbid block creations: only - * overwrites are permitted. We fall back to buffered writes - * at a higher level for inside-i_size block-instantiating - * writes. - */ ret = (*dio->get_block)(dio->inode, fs_startblk, map_bh, create); } @@ -620,10 +632,26 @@ static int dio_send_cur_page(struct dio *dio) int ret = 0; if (dio->bio) { + loff_t cur_offset = dio->block_in_file << dio->blkbits; + loff_t bio_next_offset = dio->logical_offset_in_bio + + dio->bio->bi_size; + /* - * See whether this new request is contiguous with the old + * See whether this new request is contiguous with the old. + * + * Btrfs cannot handl having logically non-contiguous requests + * submitted. For exmple if you have + * + * Logical: [0-4095][HOLE][8192-12287] + * Phyiscal: [0-4095] [4096-8181] + * + * We cannot submit those pages together as one BIO. So if our + * current logical offset in the file does not equal what would + * be the next logical offset in the bio, submit the bio we + * have. */ - if (dio->final_block_in_bio != dio->cur_page_block) + if (dio->final_block_in_bio != dio->cur_page_block || + cur_offset != bio_next_offset) dio_bio_submit(dio); /* * Submit now if the underlying fs is about to perform a @@ -674,6 +702,13 @@ 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? */ @@ -711,6 +746,7 @@ submit_page_section(struct dio *dio, struct page *page, dio->cur_page_offset = offset; dio->cur_page_len = len; dio->cur_page_block = blocknr; + dio->cur_page_fs_offset = dio->block_in_file << dio->blkbits; out: return ret; } @@ -768,7 +804,7 @@ static void dio_zero_block(struct dio *dio, int end) this_chunk_bytes = this_chunk_blocks << dio->blkbits; - page = ZERO_PAGE(dio->curr_user_address); + page = ZERO_PAGE(0); if (submit_page_section(dio, page, 0, this_chunk_bytes, dio->next_block_for_io)) return; @@ -863,11 +899,10 @@ static int do_direct_IO(struct dio *dio) do_holes: /* Handle holes */ if (!buffer_mapped(map_bh)) { - char *kaddr; loff_t i_size_aligned; /* AKPM: eargh, -ENOTBLK is a hack */ - if (dio->rw == WRITE) { + if (dio->rw & WRITE) { page_cache_release(page); return -ENOTBLK; } @@ -884,11 +919,8 @@ do_holes: page_cache_release(page); goto out; } - kaddr = kmap_atomic(page, KM_USER0); - memset(kaddr + (block_in_page << blkbits), - 0, 1 << blkbits); - flush_dcache_page(page); - kunmap_atomic(kaddr, KM_USER0); + zero_user(page, block_in_page << blkbits, + 1 << blkbits); dio->block_in_file++; block_in_page++; goto next_block; @@ -949,52 +981,32 @@ static ssize_t direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, const struct iovec *iov, loff_t offset, unsigned long nr_segs, unsigned blkbits, get_block_t get_block, dio_iodone_t end_io, - struct dio *dio) + dio_submit_t submit_io, struct dio *dio) { unsigned long user_addr; + unsigned long flags; int seg; ssize_t ret = 0; ssize_t ret2; size_t bytes; - dio->bio = NULL; dio->inode = inode; dio->rw = rw; dio->blkbits = blkbits; dio->blkfactor = inode->i_blkbits - blkbits; - dio->start_zero_done = 0; - dio->size = 0; dio->block_in_file = offset >> blkbits; - dio->blocks_available = 0; - dio->cur_page = NULL; - dio->boundary = 0; - dio->reap_counter = 0; dio->get_block = get_block; dio->end_io = end_io; - dio->map_bh.b_private = NULL; + dio->submit_io = submit_io; dio->final_block_in_bio = -1; dio->next_block_for_io = -1; - dio->page_errors = 0; - dio->io_error = 0; - dio->result = 0; 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->bio_list = NULL; - dio->waiter = NULL; + dio->refcount = 1; /* * In case of non-aligned buffers, we may need 2 more @@ -1002,8 +1014,6 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, */ if (unlikely(dio->blkfactor)) dio->pages_in_io = 2; - else - dio->pages_in_io = 0; for (seg = 0; seg < nr_segs; seg++) { user_addr = (unsigned long)iov[seg].iov_base; @@ -1045,7 +1055,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, } } /* end iovec loop */ - if (ret == -ENOTBLK && rw == WRITE) { + if (ret == -ENOTBLK) { /* * The remaining part of the request will be * be handled by buffered I/O when we return @@ -1079,107 +1089,56 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, * we can let i_mutex go now that its achieved its purpose * of protecting us from looking up uninitialized blocks. */ - if ((rw == READ) && (dio->lock_type == DIO_LOCKING)) + if (rw == READ && (dio->flags & DIO_LOCKING)) 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 */ + if (ret != -EIOCBQUEUED) { + /* All IO is now issued, send it on its way */ 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); + dio_await_completion(dio); + } - 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; + /* + * 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); - /* 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); + if (ret2 == 0) { + ret = dio_complete(dio, offset, ret); kfree(dio); - } + } else + BUG_ON(ret != -EIOCBQUEUED); + return ret; } -/* - * This is a library function for use by filesystem drivers. - * The locking rules are governed by the dio_lock_type parameter. - * - * DIO_NO_LOCKING (no locking, for raw block device access) - * For writes, i_mutex is not held on entry; it is never taken. - * - * DIO_LOCKING (simple locking for regular files) - * For writes we are called under i_mutex and return with i_mutex held, even - * though it is internally dropped. - * For reads, i_mutex is not held on entry, but it is taken and dropped before - * returning. - * - * DIO_OWN_LOCKING (filesystem provides synchronisation and handling of - * uninitialised data, allowing parallel direct readers and writers) - * For writes we are called without i_mutex, return without it, never touch it. - * For reads we are called under i_mutex and return with i_mutex held, even - * though it may be internally dropped. - * - * Additional i_alloc_sem locking requirements described inline below. - */ ssize_t -__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, +__blockdev_direct_IO_newtrunc(int rw, struct kiocb *iocb, struct inode *inode, struct block_device *bdev, const struct iovec *iov, loff_t offset, unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io, - int dio_lock_type) + dio_submit_t submit_io, int flags) { int seg; size_t size; @@ -1190,14 +1149,12 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, ssize_t retval = -EINVAL; loff_t end = offset; struct dio *dio; - int release_i_mutex = 0; - int acquire_i_mutex = 0; if (rw & WRITE) - current->flags |= PF_SYNCWRITE; + rw = WRITE_ODIRECT_PLUG; if (bdev) - bdev_blkbits = blksize_bits(bdev_hardsect_size(bdev)); + bdev_blkbits = blksize_bits(bdev_logical_block_size(bdev)); if (offset & blocksize_mask) { if (bdev) @@ -1225,43 +1182,37 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, retval = -ENOMEM; if (!dio) goto out; - /* - * For block device access DIO_NO_LOCKING is used, - * neither readers nor writers do any locking at all - * For regular files using DIO_LOCKING, - * readers need to grab i_mutex and i_alloc_sem - * writers need to grab i_alloc_sem only (i_mutex is already held) - * For regular files using DIO_OWN_LOCKING, - * neither readers nor writers take any locks here + * Believe it or not, zeroing out the page array caused a .5% + * performance regression in a database benchmark. So, we take + * care to only zero out what's needed. */ - dio->lock_type = dio_lock_type; - if (dio_lock_type != DIO_NO_LOCKING) { + memset(dio, 0, offsetof(struct dio, pages)); + + dio->flags = flags; + if (dio->flags & DIO_LOCKING) { /* watch out for a 0 len io from a tricksy fs */ if (rw == READ && end > offset) { - struct address_space *mapping; + struct address_space *mapping = + iocb->ki_filp->f_mapping; - mapping = iocb->ki_filp->f_mapping; - if (dio_lock_type != DIO_OWN_LOCKING) { - mutex_lock(&inode->i_mutex); - release_i_mutex = 1; - } + /* will be released by direct_io_worker */ + mutex_lock(&inode->i_mutex); retval = filemap_write_and_wait_range(mapping, offset, end - 1); if (retval) { + mutex_unlock(&inode->i_mutex); kfree(dio); goto out; } - - if (dio_lock_type == DIO_OWN_LOCKING) { - mutex_unlock(&inode->i_mutex); - acquire_i_mutex = 1; - } } - if (dio_lock_type == DIO_LOCKING) - down_read(&inode->i_alloc_sem); + /* + * Will be released at I/O completion, possibly in a + * different thread. + */ + down_read_non_owner(&inode->i_alloc_sem); } /* @@ -1270,22 +1221,67 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, * even for AIO, we need to wait for i/o to complete before * returning in this case. */ - dio->is_async = !is_sync_kiocb(iocb) && !((rw == WRITE) && + dio->is_async = !is_sync_kiocb(iocb) && !((rw & WRITE) && (end > i_size_read(inode))); retval = direct_io_worker(rw, iocb, inode, iov, offset, - nr_segs, blkbits, get_block, end_io, dio); - - if (rw == READ && dio_lock_type == DIO_LOCKING) - release_i_mutex = 0; + nr_segs, blkbits, get_block, end_io, + submit_io, dio); out: - if (release_i_mutex) - mutex_unlock(&inode->i_mutex); - else if (acquire_i_mutex) - mutex_lock(&inode->i_mutex); - if (rw & WRITE) - current->flags &= ~PF_SYNCWRITE; + return retval; +} +EXPORT_SYMBOL(__blockdev_direct_IO_newtrunc); + +/* + * This is a library function for use by filesystem drivers. + * + * The locking rules are governed by the flags parameter: + * - if the flags value contains DIO_LOCKING we use a fancy locking + * scheme for dumb filesystems. + * For writes this function is called under i_mutex and returns with + * i_mutex held, for reads, i_mutex is not held on entry, but it is + * taken and dropped again before returning. + * For reads and writes i_alloc_sem is taken in shared mode and released + * on I/O completion (which may happen asynchronously after returning to + * the caller). + * + * - if the flags value does NOT contain DIO_LOCKING we don't use any + * internal locking but rather rely on the filesystem to synchronize + * direct I/O reads/writes versus each other and truncate. + * For reads and writes both i_mutex and i_alloc_sem are not held on + * entry and are never taken. + */ +ssize_t +__blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *inode, + struct block_device *bdev, const struct iovec *iov, loff_t offset, + unsigned long nr_segs, get_block_t get_block, dio_iodone_t end_io, + dio_submit_t submit_io, int flags) +{ + ssize_t retval; + + retval = __blockdev_direct_IO_newtrunc(rw, iocb, inode, bdev, iov, + offset, nr_segs, get_block, end_io, submit_io, flags); + /* + * In case of error extending write may have instantiated a few + * blocks outside i_size. Trim these off again for DIO_LOCKING. + * NOTE: DIO_NO_LOCK/DIO_OWN_LOCK callers have to handle this in + * their own manner. This is a further example of where the old + * truncate sequence is inadequate. + * + * NOTE: filesystems with their own locking have to handle this + * on their own. + */ + if (flags & DIO_LOCKING) { + if (unlikely((rw & WRITE) && retval < 0)) { + loff_t isize = i_size_read(inode); + loff_t end = offset + iov_length(iov, nr_segs); + + if (end > isize) + vmtruncate(inode, isize); + } + } + return retval; } EXPORT_SYMBOL(__blockdev_direct_IO);