diff options
Diffstat (limited to 'fs/direct-io.c')
| -rw-r--r-- | fs/direct-io.c | 1332 |
1 files changed, 1332 insertions, 0 deletions
diff --git a/fs/direct-io.c b/fs/direct-io.c new file mode 100644 index 000000000..745d23426 --- /dev/null +++ b/fs/direct-io.c @@ -0,0 +1,1332 @@ +/* + * fs/direct-io.c + * + * Copyright (C) 2002, Linus Torvalds. + * + * O_DIRECT + * + * 04Jul2002 Andrew Morton + * Initial version + * 11Sep2002 janetinc@us.ibm.com + * added readv/writev support. + * 29Oct2002 Andrew Morton + * rewrote bio_add_page() support. + * 30Oct2002 pbadari@us.ibm.com + * added support for non-aligned IO. + * 06Nov2002 pbadari@us.ibm.com + * added asynchronous IO support. + * 21Jul2003 nathans@sgi.com + * added IO completion notifier. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/types.h> +#include <linux/fs.h> +#include <linux/mm.h> +#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> +#include <linux/blkdev.h> +#include <linux/buffer_head.h> +#include <linux/rwsem.h> +#include <linux/uio.h> +#include <linux/atomic.h> +#include <linux/prefetch.h> + +/* + * How many user pages to map in one call to get_user_pages(). This determines + * the size of a structure in the slab cache + */ +#define DIO_PAGES 64 + +/* + * This code generally works in units of "dio_blocks". A dio_block is + * somewhere between the hard sector size and the filesystem block size. it + * is determined on a per-invocation basis. When talking to the filesystem + * we need to convert dio_blocks to fs_blocks by scaling the dio_block quantity + * down by dio->blkfactor. Similarly, fs-blocksize quantities are converted + * to bio_block quantities by shifting left by blkfactor. + * + * If blkfactor is zero then the user's request was aligned to the filesystem's + * blocksize. + */ + +/* dio_state only used in the submission path */ + +struct dio_submit { + struct bio *bio; /* bio under assembly */ + unsigned blkbits; /* doesn't change */ + unsigned blkfactor; /* When we're using an alignment which + is finer than the filesystem's soft + blocksize, this specifies how much + finer. blkfactor=2 means 1/4-block + alignment. Does not change */ + unsigned start_zero_done; /* flag: sub-blocksize zeroing has + been performed at the start of a + write */ + int pages_in_io; /* approximate total IO pages */ + sector_t block_in_file; /* Current offset into the underlying + file in dio_block units. */ + unsigned blocks_available; /* At block_in_file. changes */ + int reap_counter; /* rate limit reaping */ + sector_t final_block_in_request;/* doesn't change */ + int boundary; /* prev block is at a boundary */ + get_block_t *get_block; /* block mapping 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 */ + + /* + * Deferred addition of a page to the dio. These variables are + * private to dio_send_cur_page(), submit_page_section() and + * dio_bio_add_page(). + */ + struct page *cur_page; /* The page */ + 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 */ + + struct iov_iter *iter; + /* + * Page queue. These variables belong to dio_refill_pages() and + * dio_get_page(). + */ + unsigned head; /* next page to process */ + unsigned tail; /* last valid page + 1 */ + size_t from, to; +}; + +/* dio_state communicated between submission path and end_io */ +struct dio { + int flags; /* doesn't change */ + int rw; + struct inode *inode; + loff_t i_size; /* i_size when submitted */ + dio_iodone_t *end_io; /* IO completion function */ + + void *private; /* copy from map_bh.b_private */ + + /* BIO completion state */ + 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 */ + struct task_struct *waiter; /* waiting task (NULL if none) */ + + /* AIO related stuff */ + struct kiocb *iocb; /* kiocb */ + 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. + */ + 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; + +/* + * How many pages are in the queue? + */ +static inline unsigned dio_pages_present(struct dio_submit *sdio) +{ + return sdio->tail - sdio->head; +} + +/* + * Go grab and pin some userspace pages. Typically we'll get 64 at a time. + */ +static inline int dio_refill_pages(struct dio *dio, struct dio_submit *sdio) +{ + ssize_t ret; + + ret = iov_iter_get_pages(sdio->iter, dio->pages, LONG_MAX, DIO_PAGES, + &sdio->from); + + if (ret < 0 && sdio->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 + * leaking stale data in the file. + */ + if (dio->page_errors == 0) + dio->page_errors = ret; + page_cache_get(page); + dio->pages[0] = page; + sdio->head = 0; + sdio->tail = 1; + sdio->from = 0; + sdio->to = PAGE_SIZE; + return 0; + } + + if (ret >= 0) { + iov_iter_advance(sdio->iter, ret); + ret += sdio->from; + sdio->head = 0; + sdio->tail = (ret + PAGE_SIZE - 1) / PAGE_SIZE; + sdio->to = ((ret - 1) & (PAGE_SIZE - 1)) + 1; + return 0; + } + return ret; +} + +/* + * Get another userspace page. Returns an ERR_PTR on error. Pages are + * buffered inside the dio so that we can call get_user_pages() against a + * decent number of pages, less frequently. To provide nicer use of the + * L1 cache. + */ +static inline struct page *dio_get_page(struct dio *dio, + struct dio_submit *sdio) +{ + if (dio_pages_present(sdio) == 0) { + int ret; + + ret = dio_refill_pages(dio, sdio); + if (ret) + return ERR_PTR(ret); + BUG_ON(dio_pages_present(sdio) == 0); + } + return dio->pages[sdio->head]; +} + +/** + * dio_complete() - called when all DIO BIO I/O has been completed + * @offset: the byte offset in the file of the completed 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) +{ + ssize_t transferred = 0; + + /* + * 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; + + if (dio->result) { + transferred = dio->result; + + /* Check for short read case */ + if ((dio->rw == READ) && ((offset + transferred) > dio->i_size)) + transferred = dio->i_size - offset; + } + + if (ret == 0) + ret = dio->page_errors; + if (ret == 0) + ret = dio->io_error; + if (ret == 0) + ret = transferred; + + if (dio->end_io && dio->result) + dio->end_io(dio->iocb, offset, transferred, dio->private); + + if (!(dio->flags & DIO_SKIP_DIO_COUNT)) + inode_dio_end(dio->inode); + + 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; + } + + dio->iocb->ki_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. + */ +static void dio_bio_end_aio(struct bio *bio, int error) +{ + struct dio *dio = bio->bi_private; + unsigned long remaining; + unsigned long flags; + + /* 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) { + 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); + } + } +} + +/* + * The BIO completion handler simply queues the BIO up for the process-context + * handler. + * + * 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 void dio_bio_end_io(struct bio *bio, int error) +{ + struct dio *dio = bio->bi_private; + unsigned long flags; + + 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); +} + +/** + * 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 inline void +dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, + struct block_device *bdev, + sector_t first_sector, int nr_vecs) +{ + struct bio *bio; + + /* + * bio_alloc() is guaranteed to return a bio when called with + * __GFP_WAIT and we request a valid number of vectors. + */ + bio = bio_alloc(GFP_KERNEL, nr_vecs); + + bio->bi_bdev = bdev; + bio->bi_iter.bi_sector = first_sector; + if (dio->is_async) + bio->bi_end_io = dio_bio_end_aio; + else + bio->bi_end_io = dio_bio_end_io; + + sdio->bio = bio; + sdio->logical_offset_in_bio = sdio->cur_page_fs_offset; +} + +/* + * 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 inline void dio_bio_submit(struct dio *dio, struct dio_submit *sdio) +{ + struct bio *bio = sdio->bio; + unsigned long flags; + + bio->bi_private = dio; + + 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); + + if (sdio->submit_io) + sdio->submit_io(dio->rw, bio, dio->inode, + sdio->logical_offset_in_bio); + else + submit_bio(dio->rw, bio); + + sdio->bio = NULL; + sdio->boundary = 0; + sdio->logical_offset_in_bio = 0; +} + +/* + * Release any resources in case of a failure + */ +static inline void dio_cleanup(struct dio *dio, struct dio_submit *sdio) +{ + while (sdio->head < sdio->tail) + page_cache_release(dio->pages[sdio->head++]); +} + +/* + * 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 = NULL; + + spin_lock_irqsave(&dio->bio_lock, flags); + + /* + * 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; + } + spin_unlock_irqrestore(&dio->bio_lock, flags); + return bio; +} + +/* + * Process one completed BIO. No locks are held. + */ +static int dio_bio_complete(struct dio *dio, struct bio *bio) +{ + const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags); + struct bio_vec *bvec; + unsigned i; + + if (!uptodate) + dio->io_error = -EIO; + + if (dio->is_async && dio->rw == READ) { + bio_check_pages_dirty(bio); /* transfers ownership */ + } else { + bio_for_each_segment_all(bvec, bio, i) { + struct page *page = bvec->bv_page; + + if (dio->rw == READ && !PageCompound(page)) + set_page_dirty_lock(page); + page_cache_release(page); + } + bio_put(bio); + } + return uptodate ? 0 : -EIO; +} + +/* + * 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 void dio_await_completion(struct dio *dio) +{ + struct bio *bio; + do { + bio = dio_await_one(dio); + if (bio) + dio_bio_complete(dio, bio); + } while (bio); +} + +/* + * A really large O_DIRECT read or write can generate a lot of BIOs. So + * to keep the memory consumption sane we periodically reap any completed BIOs + * during the BIO generation phase. + * + * This also helps to limit the peak amount of pinned userspace memory. + */ +static inline int dio_bio_reap(struct dio *dio, struct dio_submit *sdio) +{ + int ret = 0; + + if (sdio->reap_counter++ >= 64) { + while (dio->bio_list) { + unsigned long flags; + struct bio *bio; + int ret2; + + spin_lock_irqsave(&dio->bio_lock, flags); + bio = dio->bio_list; + dio->bio_list = bio->bi_private; + spin_unlock_irqrestore(&dio->bio_lock, flags); + ret2 = dio_bio_complete(dio, bio); + if (ret == 0) + ret = ret2; + } + sdio->reap_counter = 0; + } + 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 *old; + 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 + */ + old = cmpxchg(&sb->s_dio_done_wq, NULL, wq); + /* Someone created workqueue before us? Free ours... */ + if (old) + 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 + * fs blocksize, (1 << inode->i_blkbits). + * + * The fs is allowed to map lots of blocks at once. If it wants to do that, + * it uses the passed inode-relative block number as the file offset, as usual. + * + * get_block() is passed the number of i_blkbits-sized blocks which direct_io + * has remaining to do. The fs should not map more than this number of blocks. + * + * If the fs has mapped a lot of blocks, it should populate bh->b_size to + * indicate how much contiguous disk space has been made available at + * bh->b_blocknr. + * + * If *any* of the mapped blocks are new, then the fs must set buffer_new(). + * This isn't very efficient... + * + * In the case of filesystem holes: the fs may return an arbitrarily-large + * hole by returning an appropriate value in b_size and by clearing + * buffer_mapped(). However the direct-io code will only process holes one + * block at a time - it will repeatedly call get_block() as it walks the hole. + */ +static int get_more_blocks(struct dio *dio, struct dio_submit *sdio, + struct buffer_head *map_bh) +{ + int ret; + sector_t fs_startblk; /* Into file, in filesystem-sized blocks */ + sector_t fs_endblk; /* Into file, in filesystem-sized blocks */ + unsigned long fs_count; /* Number of filesystem-sized blocks */ + int create; + unsigned int i_blkbits = sdio->blkbits + sdio->blkfactor; + + /* + * If there was a memory error and we've overwritten all the + * mapped blocks then we can now return that memory error + */ + ret = dio->page_errors; + if (ret == 0) { + BUG_ON(sdio->block_in_file >= sdio->final_block_in_request); + fs_startblk = sdio->block_in_file >> sdio->blkfactor; + fs_endblk = (sdio->final_block_in_request - 1) >> + sdio->blkfactor; + fs_count = fs_endblk - fs_startblk + 1; + + map_bh->b_state = 0; + map_bh->b_size = fs_count << 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->flags & DIO_SKIP_HOLES) { + if (sdio->block_in_file < (i_size_read(dio->inode) >> + sdio->blkbits)) + create = 0; + } + + ret = (*sdio->get_block)(dio->inode, fs_startblk, + map_bh, create); + + /* 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; +} + +/* + * There is no bio. Make one now. + */ +static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio, + sector_t start_sector, struct buffer_head *map_bh) +{ + sector_t sector; + int ret, nr_pages; + + ret = dio_bio_reap(dio, sdio); + if (ret) + goto out; + sector = start_sector << (sdio->blkbits - 9); + nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(map_bh->b_bdev)); + BUG_ON(nr_pages <= 0); + dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages); + sdio->boundary = 0; +out: + return ret; +} + +/* + * Attempt to put the current chunk of 'cur_page' into the current BIO. If + * that was successful then update final_block_in_bio and take a ref against + * the just-added page. + * + * Return zero on success. Non-zero means the caller needs to start a new BIO. + */ +static inline int dio_bio_add_page(struct dio_submit *sdio) +{ + int ret; + + ret = bio_add_page(sdio->bio, sdio->cur_page, + sdio->cur_page_len, sdio->cur_page_offset); + if (ret == sdio->cur_page_len) { + /* + * Decrement count only, if we are done with this page + */ + if ((sdio->cur_page_len + sdio->cur_page_offset) == PAGE_SIZE) + sdio->pages_in_io--; + page_cache_get(sdio->cur_page); + sdio->final_block_in_bio = sdio->cur_page_block + + (sdio->cur_page_len >> sdio->blkbits); + ret = 0; + } else { + ret = 1; + } + return ret; +} + +/* + * Put cur_page under IO. The section of cur_page which is described by + * cur_page_offset,cur_page_len is put into a BIO. The section of cur_page + * starts on-disk at cur_page_block. + * + * We take a ref against the page here (on behalf of its presence in the bio). + * + * The caller of this function is responsible for removing cur_page from the + * dio, and for dropping the refcount which came from that presence. + */ +static inline int dio_send_cur_page(struct dio *dio, struct dio_submit *sdio, + struct buffer_head *map_bh) +{ + int ret = 0; + + if (sdio->bio) { + loff_t cur_offset = sdio->cur_page_fs_offset; + loff_t bio_next_offset = sdio->logical_offset_in_bio + + sdio->bio->bi_iter.bi_size; + + /* + * See whether this new request is contiguous with the old. + * + * Btrfs cannot handle having logically non-contiguous requests + * submitted. For example if you have + * + * Logical: [0-4095][HOLE][8192-12287] + * Physical: [0-4095] [4096-8191] + * + * 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 (sdio->final_block_in_bio != sdio->cur_page_block || + cur_offset != bio_next_offset) + dio_bio_submit(dio, sdio); + } + + if (sdio->bio == NULL) { + ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); + if (ret) + goto out; + } + + if (dio_bio_add_page(sdio) != 0) { + dio_bio_submit(dio, sdio); + ret = dio_new_bio(dio, sdio, sdio->cur_page_block, map_bh); + if (ret == 0) { + ret = dio_bio_add_page(sdio); + BUG_ON(ret != 0); + } + } +out: + return ret; +} + +/* + * An autonomous function to put a chunk of a page under deferred IO. + * + * The caller doesn't actually know (or care) whether this piece of page is in + * a BIO, or is under IO or whatever. We just take care of all possible + * situations here. The separation between the logic of do_direct_IO() and + * that of submit_page_section() is important for clarity. Please don't break. + * + * The chunk of page starts on-disk at blocknr. + * + * We perform deferred IO, by recording the last-submitted page inside our + * private part of the dio structure. If possible, we just expand the IO + * across that page here. + * + * If that doesn't work out then we put the old page into the bio and add this + * page to the dio instead. + */ +static inline int +submit_page_section(struct dio *dio, struct dio_submit *sdio, struct page *page, + unsigned offset, unsigned len, sector_t blocknr, + struct buffer_head *map_bh) +{ + 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? + */ + if (sdio->cur_page == page && + sdio->cur_page_offset + sdio->cur_page_len == offset && + sdio->cur_page_block + + (sdio->cur_page_len >> sdio->blkbits) == blocknr) { + sdio->cur_page_len += len; + goto out; + } + + /* + * If there's a deferred page already there then send it. + */ + if (sdio->cur_page) { + ret = dio_send_cur_page(dio, sdio, map_bh); + page_cache_release(sdio->cur_page); + sdio->cur_page = NULL; + if (ret) + return ret; + } + + page_cache_get(page); /* It is in dio */ + sdio->cur_page = page; + sdio->cur_page_offset = offset; + sdio->cur_page_len = len; + sdio->cur_page_block = blocknr; + sdio->cur_page_fs_offset = sdio->block_in_file << sdio->blkbits; +out: + /* + * If sdio->boundary then we want to schedule the IO now to + * avoid metadata seeks. + */ + if (sdio->boundary) { + ret = dio_send_cur_page(dio, sdio, map_bh); + dio_bio_submit(dio, sdio); + page_cache_release(sdio->cur_page); + sdio->cur_page = NULL; + } + return ret; +} + +/* + * Clean any dirty buffers in the blockdev mapping which alias newly-created + * file blocks. Only called for S_ISREG files - blockdevs do not set + * buffer_new + */ +static void clean_blockdev_aliases(struct dio *dio, struct buffer_head *map_bh) +{ + unsigned i; + unsigned nblocks; + + nblocks = map_bh->b_size >> dio->inode->i_blkbits; + + for (i = 0; i < nblocks; i++) { + unmap_underlying_metadata(map_bh->b_bdev, + map_bh->b_blocknr + i); + } +} + +/* + * If we are not writing the entire block and get_block() allocated + * the block for us, we need to fill-in the unused portion of the + * block with zeros. This happens only if user-buffer, fileoffset or + * io length is not filesystem block-size multiple. + * + * `end' is zero if we're doing the start of the IO, 1 at the end of the + * IO. + */ +static inline void dio_zero_block(struct dio *dio, struct dio_submit *sdio, + int end, struct buffer_head *map_bh) +{ + unsigned dio_blocks_per_fs_block; + unsigned this_chunk_blocks; /* In dio_blocks */ + unsigned this_chunk_bytes; + struct page *page; + + sdio->start_zero_done = 1; + if (!sdio->blkfactor || !buffer_new(map_bh)) + return; + + dio_blocks_per_fs_block = 1 << sdio->blkfactor; + this_chunk_blocks = sdio->block_in_file & (dio_blocks_per_fs_block - 1); + + if (!this_chunk_blocks) + return; + + /* + * We need to zero out part of an fs block. It is either at the + * beginning or the end of the fs block. + */ + if (end) + this_chunk_blocks = dio_blocks_per_fs_block - this_chunk_blocks; + + this_chunk_bytes = this_chunk_blocks << sdio->blkbits; + + page = ZERO_PAGE(0); + if (submit_page_section(dio, sdio, page, 0, this_chunk_bytes, + sdio->next_block_for_io, map_bh)) + return; + + sdio->next_block_for_io += this_chunk_blocks; +} + +/* + * Walk the user pages, and the file, mapping blocks to disk and generating + * a sequence of (page,offset,len,block) mappings. These mappings are injected + * into submit_page_section(), which takes care of the next stage of submission + * + * Direct IO against a blockdev is different from a file. Because we can + * happily perform page-sized but 512-byte aligned IOs. It is important that + * blockdev IO be able to have fine alignment and large sizes. + * + * So what we do is to permit the ->get_block function to populate bh.b_size + * with the size of IO which is permitted at this offset and this i_blkbits. + * + * For best results, the blockdev should be set up with 512-byte i_blkbits and + * it should set b_size to PAGE_SIZE or more inside get_block(). This gives + * fine alignment but still allows this function to work in PAGE_SIZE units. + */ +static int do_direct_IO(struct dio *dio, struct dio_submit *sdio, + struct buffer_head *map_bh) +{ + const unsigned blkbits = sdio->blkbits; + int ret = 0; + + while (sdio->block_in_file < sdio->final_block_in_request) { + struct page *page; + size_t from, to; + + page = dio_get_page(dio, sdio); + if (IS_ERR(page)) { + ret = PTR_ERR(page); + goto out; + } + from = sdio->head ? 0 : sdio->from; + to = (sdio->head == sdio->tail - 1) ? sdio->to : PAGE_SIZE; + sdio->head++; + + while (from < to) { + unsigned this_chunk_bytes; /* # of bytes mapped */ + unsigned this_chunk_blocks; /* # of blocks */ + unsigned u; + + if (sdio->blocks_available == 0) { + /* + * Need to go and map some more disk + */ + unsigned long blkmask; + unsigned long dio_remainder; + + ret = get_more_blocks(dio, sdio, map_bh); + if (ret) { + page_cache_release(page); + goto out; + } + if (!buffer_mapped(map_bh)) + goto do_holes; + + sdio->blocks_available = + map_bh->b_size >> sdio->blkbits; + sdio->next_block_for_io = + map_bh->b_blocknr << sdio->blkfactor; + if (buffer_new(map_bh)) + clean_blockdev_aliases(dio, map_bh); + + if (!sdio->blkfactor) + goto do_holes; + + blkmask = (1 << sdio->blkfactor) - 1; + dio_remainder = (sdio->block_in_file & blkmask); + + /* + * If we are at the start of IO and that IO + * starts partway into a fs-block, + * dio_remainder will be non-zero. If the IO + * is a read then we can simply advance the IO + * cursor to the first block which is to be + * read. But if the IO is a write and the + * block was newly allocated we cannot do that; + * the start of the fs block must be zeroed out + * on-disk + */ + if (!buffer_new(map_bh)) + sdio->next_block_for_io += dio_remainder; + sdio->blocks_available -= dio_remainder; + } +do_holes: + /* Handle holes */ + if (!buffer_mapped(map_bh)) { + loff_t i_size_aligned; + + /* AKPM: eargh, -ENOTBLK is a hack */ + if (dio->rw & WRITE) { + page_cache_release(page); + return -ENOTBLK; + } + + /* + * Be sure to account for a partial block as the + * last block in the file + */ + i_size_aligned = ALIGN(i_size_read(dio->inode), + 1 << blkbits); + if (sdio->block_in_file >= + i_size_aligned >> blkbits) { + /* We hit eof */ + page_cache_release(page); + goto out; + } + zero_user(page, from, 1 << blkbits); + sdio->block_in_file++; + from += 1 << blkbits; + dio->result += 1 << blkbits; + goto next_block; + } + + /* + * If we're performing IO which has an alignment which + * is finer than the underlying fs, go check to see if + * we must zero out the start of this block. + */ + if (unlikely(sdio->blkfactor && !sdio->start_zero_done)) + dio_zero_block(dio, sdio, 0, map_bh); + + /* + * Work out, in this_chunk_blocks, how much disk we + * can add to this page + */ + this_chunk_blocks = sdio->blocks_available; + u = (to - from) >> blkbits; + if (this_chunk_blocks > u) + this_chunk_blocks = u; + u = sdio->final_block_in_request - sdio->block_in_file; + if (this_chunk_blocks > u) + this_chunk_blocks = u; + this_chunk_bytes = this_chunk_blocks << blkbits; + BUG_ON(this_chunk_bytes == 0); + + if (this_chunk_blocks == sdio->blocks_available) + sdio->boundary = buffer_boundary(map_bh); + ret = submit_page_section(dio, sdio, page, + from, + this_chunk_bytes, + sdio->next_block_for_io, + map_bh); + if (ret) { + page_cache_release(page); + goto out; + } + sdio->next_block_for_io += this_chunk_blocks; + + sdio->block_in_file += this_chunk_blocks; + from += this_chunk_bytes; + dio->result += this_chunk_bytes; + sdio->blocks_available -= this_chunk_blocks; +next_block: + BUG_ON(sdio->block_in_file > sdio->final_block_in_request); + if (sdio->block_in_file == sdio->final_block_in_request) + break; + } + + /* Drop the ref which was taken in get_user_pages() */ + page_cache_release(page); + } +out: + return ret; +} + +static inline int drop_refcount(struct dio *dio) +{ + int ret2; + unsigned long flags; + + /* + * 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 ->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); + return ret2; +} + +/* + * 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. + * - 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. + * + * To help with locking against truncate we incremented the i_dio_count + * counter before starting direct I/O, and decrement it once we are done. + * Truncate can wait for it to reach zero to provide exclusion. It is + * expected that filesystem provide exclusion between new direct I/O + * and truncates. For DIO_LOCKING filesystems this is done by i_mutex, + * but other filesystems need to take care of this on their own. + * + * NOTE: if you pass "sdio" to anything by pointer make sure that function + * is always inlined. Otherwise gcc is unable to split the structure into + * individual fields and will generate much worse code. This is important + * for the whole file. + */ +static inline ssize_t +do_blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, + struct block_device *bdev, struct iov_iter *iter, + loff_t offset, get_block_t get_block, dio_iodone_t end_io, + dio_submit_t submit_io, int flags) +{ + unsigned i_blkbits = ACCESS_ONCE(inode->i_blkbits); + unsigned blkbits = i_blkbits; + unsigned blocksize_mask = (1 << blkbits) - 1; + ssize_t retval = -EINVAL; + size_t count = iov_iter_count(iter); + loff_t end = offset + count; + struct dio *dio; + struct dio_submit sdio = { 0, }; + struct buffer_head map_bh = { 0, }; + struct blk_plug plug; + unsigned long align = offset | iov_iter_alignment(iter); + + /* + * Avoid references to bdev if not absolutely needed to give + * the early prefetch in the caller enough time. + */ + + if (align & blocksize_mask) { + if (bdev) + blkbits = blksize_bits(bdev_logical_block_size(bdev)); + blocksize_mask = (1 << blkbits) - 1; + if (align & blocksize_mask) + goto out; + } + + /* watch out for a 0 len io from a tricksy fs */ + if (iov_iter_rw(iter) == READ && !iov_iter_count(iter)) + return 0; + + dio = kmem_cache_alloc(dio_cache, GFP_KERNEL); + retval = -ENOMEM; + if (!dio) + goto out; + /* + * 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. + */ + memset(dio, 0, offsetof(struct dio, pages)); + + dio->flags = flags; + if (dio->flags & DIO_LOCKING) { + if (iov_iter_rw(iter) == READ) { + struct address_space *mapping = + iocb->ki_filp->f_mapping; + + /* 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); + kmem_cache_free(dio_cache, dio); + goto out; + } + } + } + + /* + * For file extending writes updating i_size before data writeouts + * complete can expose uninitialized blocks in dumb filesystems. + * In that case we need to wait for I/O completion even if asked + * for an asynchronous write. + */ + if (is_sync_kiocb(iocb)) + dio->is_async = false; + else if (!(dio->flags & DIO_ASYNC_EXTEND) && + iov_iter_rw(iter) == WRITE && end > i_size_read(inode)) + dio->is_async = false; + else + dio->is_async = true; + + dio->inode = inode; + dio->rw = iov_iter_rw(iter) == WRITE ? WRITE_ODIRECT : READ; + + /* + * For AIO O_(D)SYNC writes we need to defer completions to a workqueue + * so that we can call ->fsync. + */ + if (dio->is_async && iov_iter_rw(iter) == 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. + */ + if (!(dio->flags & DIO_SKIP_DIO_COUNT)) + inode_dio_begin(inode); + + retval = 0; + sdio.blkbits = blkbits; + sdio.blkfactor = i_blkbits - blkbits; + sdio.block_in_file = offset >> blkbits; + + sdio.get_block = get_block; + dio->end_io = end_io; + sdio.submit_io = submit_io; + sdio.final_block_in_bio = -1; + sdio.next_block_for_io = -1; + + dio->iocb = iocb; + dio->i_size = i_size_read(inode); + + spin_lock_init(&dio->bio_lock); + dio->refcount = 1; + + sdio.iter = iter; + sdio.final_block_in_request = + (offset + iov_iter_count(iter)) >> blkbits; + + /* + * In case of non-aligned buffers, we may need 2 more + * pages since we need to zero out first and last block. + */ + if (unlikely(sdio.blkfactor)) + sdio.pages_in_io = 2; + + sdio.pages_in_io += iov_iter_npages(iter, INT_MAX); + + blk_start_plug(&plug); + + retval = do_direct_IO(dio, &sdio, &map_bh); + if (retval) + dio_cleanup(dio, &sdio); + + if (retval == -ENOTBLK) { + /* + * The remaining part of the request will be + * be handled by buffered I/O when we return + */ + retval = 0; + } + /* + * There may be some unwritten disk at the end of a part-written + * fs-block-sized block. Go zero that now. + */ + dio_zero_block(dio, &sdio, 1, &map_bh); + + if (sdio.cur_page) { + ssize_t ret2; + + ret2 = dio_send_cur_page(dio, &sdio, &map_bh); + if (retval == 0) + retval = ret2; + page_cache_release(sdio.cur_page); + sdio.cur_page = NULL; + } + if (sdio.bio) + dio_bio_submit(dio, &sdio); + + blk_finish_plug(&plug); + + /* + * 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. + */ + dio_cleanup(dio, &sdio); + + /* + * All block lookups have been performed. For READ requests + * we can let i_mutex go now that its achieved its purpose + * of protecting us from looking up uninitialized blocks. + */ + if (iov_iter_rw(iter) == READ && (dio->flags & DIO_LOCKING)) + mutex_unlock(&dio->inode->i_mutex); + + /* + * 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. + */ + BUG_ON(retval == -EIOCBQUEUED); + if (dio->is_async && retval == 0 && dio->result && + (iov_iter_rw(iter) == READ || dio->result == count)) + retval = -EIOCBQUEUED; + else + dio_await_completion(dio); + + if (drop_refcount(dio) == 0) { + retval = dio_complete(dio, offset, retval, false); + } else + BUG_ON(retval != -EIOCBQUEUED); + +out: + return retval; +} + +ssize_t __blockdev_direct_IO(struct kiocb *iocb, struct inode *inode, + struct block_device *bdev, struct iov_iter *iter, + loff_t offset, get_block_t get_block, + dio_iodone_t end_io, dio_submit_t submit_io, + int flags) +{ + /* + * The block device state is needed in the end to finally + * submit everything. Since it's likely to be cache cold + * prefetch it here as first thing to hide some of the + * latency. + * + * Attempt to prefetch the pieces we likely need later. + */ + prefetch(&bdev->bd_disk->part_tbl); + prefetch(bdev->bd_queue); + prefetch((char *)bdev->bd_queue + SMP_CACHE_BYTES); + + return do_blockdev_direct_IO(iocb, inode, bdev, iter, offset, get_block, + end_io, submit_io, flags); +} + +EXPORT_SYMBOL(__blockdev_direct_IO); + +static __init int dio_init(void) +{ + dio_cache = KMEM_CACHE(dio, SLAB_PANIC); + return 0; +} +module_init(dio_init) |