X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=fs%2Fdirect-io.c;h=e82adc2debb73de9ae9ca916e65c6e2bed317ef2;hb=d74340d31bf1dbeb00acadddd8697666528a7846;hp=52bb2638f7ab703e9a3d5205b097ddbf90a071e2;hpb=fcb82f8835c1d71b4fe5de1d9894f45370f80dab;p=safe%2Fjmp%2Flinux-2.6 diff --git a/fs/direct-io.c b/fs/direct-io.c index 52bb263..e82adc2 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. @@ -53,13 +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 { @@ -68,7 +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 @@ -104,6 +97,18 @@ struct dio { unsigned cur_page_len; /* Nr of bytes at cur_page_offset */ sector_t cur_page_block; /* Where it starts */ + /* 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(). */ @@ -115,22 +120,16 @@ 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 */ - 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 */ + /* + * 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 +149,14 @@ 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); + 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 @@ -246,7 +239,8 @@ static int dio_complete(struct dio *dio, loff_t offset, int ret) if (dio->end_io && dio->result) dio->end_io(dio->iocb, offset, transferred, dio->map_bh.b_private); - if (dio->lock_type == DIO_LOCKING) + + if (dio->flags & DIO_LOCKING) /* lockdep: non-owner release */ up_read_non_owner(&dio->inode->i_alloc_sem); @@ -264,15 +258,12 @@ 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; unsigned long remaining; unsigned long flags; - if (bio->bi_size) - return 1; - /* cleanup the bio */ dio_bio_complete(dio, bio); @@ -287,8 +278,6 @@ static int dio_bio_end_aio(struct bio *bio, unsigned int bytes_done, int error) aio_complete(dio->iocb, ret, 0); kfree(dio); } - - return 0; } /* @@ -298,21 +287,17 @@ 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; if (--dio->refcount == 1 && dio->waiter) wake_up_process(dio->waiter); spin_unlock_irqrestore(&dio->bio_lock, flags); - return 0; } static int @@ -322,8 +307,6 @@ 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; @@ -532,21 +515,24 @@ static int get_more_blocks(struct dio *dio) map_bh->b_state = 0; map_bh->b_size = fs_count << dio->inode->i_blkbits; + /* + * 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->lock_type == DIO_LOCKING) { + 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); } @@ -772,7 +758,7 @@ 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; @@ -887,8 +873,8 @@ do_holes: page_cache_release(page); goto out; } - zero_user_page(page, block_in_page << blkbits, - 1 << blkbits, KM_USER0); + zero_user(page, block_in_page << blkbits, + 1 << blkbits); dio->block_in_file++; block_in_page++; goto next_block; @@ -958,35 +944,22 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, 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->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); spin_lock_init(&dio->bio_lock); dio->refcount = 1; - dio->bio_list = NULL; - dio->waiter = NULL; /* * In case of non-aligned buffers, we may need 2 more @@ -994,8 +967,6 @@ 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; @@ -1060,9 +1031,6 @@ 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. @@ -1074,7 +1042,7 @@ 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); /* @@ -1089,8 +1057,11 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, ((rw & READ) || (dio->result == dio->size))) ret = -EIOCBQUEUED; - if (ret != -EIOCBQUEUED) + if (ret != -EIOCBQUEUED) { + /* All IO is now issued, send it on its way */ + blk_run_address_space(inode->i_mapping); dio_await_completion(dio); + } /* * Sync will always be dropping the final ref and completing the @@ -1118,30 +1089,28 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode, /* * 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. + * 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). * - * Additional i_alloc_sem locking requirements described inline below. + * - 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, - int dio_lock_type) + int flags) { int seg; size_t size; @@ -1152,14 +1121,12 @@ __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) - rw = WRITE_SYNC; + 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) @@ -1187,44 +1154,37 @@ __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) - /* lockdep: not the owner will release it */ - down_read_non_owner(&inode->i_alloc_sem); + /* + * Will be released at I/O completion, possibly in a + * different thread. + */ + down_read_non_owner(&inode->i_alloc_sem); } /* @@ -1239,14 +1199,22 @@ __blockdev_direct_IO(int rw, struct kiocb *iocb, struct inode *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; + /* + * In case of error extending write may have instantiated a few + * blocks outside i_size. Trim these off again for DIO_LOCKING. + * + * 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); + if (end > isize) + vmtruncate(inode, isize); + } + } out: - if (release_i_mutex) - mutex_unlock(&inode->i_mutex); - else if (acquire_i_mutex) - mutex_lock(&inode->i_mutex); return retval; } EXPORT_SYMBOL(__blockdev_direct_IO);