cregit-Linux how code gets into the kernel

Release 4.10 fs/direct-io.c

Directory: fs
 * fs/direct-io.c
 * Copyright (C) 2002, Linus Torvalds.
 * 04Jul2002    Andrew Morton
 *              Initial version
 * 11Sep2002
 *              added readv/writev support.
 * 29Oct2002    Andrew Morton
 *              rewrote bio_add_page() support.
 * 30Oct2002
 *              added support for non-aligned IO.
 * 06Nov2002
 *              added asynchronous IO support.
 * 21Jul2003
 *              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 op;
int op_flags;
blk_qc_t bio_cookie;
struct block_device *bio_bdev;
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? */
bool should_dirty;		/* if pages should be dirtied */
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 */

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; }


andrew mortonandrew morton1780.95%266.67%
andi kleenandi kleen419.05%133.33%

/* * 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->op == REQ_OP_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; get_page(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; }


andrew mortonandrew morton10553.30%327.27%
al viroal viro5728.93%19.09%
nick pigginnick piggin157.61%218.18%
andi kleenandi kleen147.11%218.18%
michael christiemichael christie31.52%19.09%
miklos szeredimiklos szeredi21.02%19.09%
kirill a. shutemovkirill a. shutemov10.51%19.09%

/* * 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]; }


andrew mortonandrew morton5981.94%125.00%
andi kleenandi kleen1013.89%250.00%
boaz harroshboaz harrosh34.17%125.00%

/** * 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, ssize_t ret, bool is_async) { loff_t offset = dio->iocb->ki_pos; 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->op == REQ_OP_READ) && ((offset + transferred) > dio->i_size)) transferred = dio->i_size - offset; /* ignore EFAULT if some IO has been done */ if (unlikely(ret == -EFAULT) && transferred) ret = 0; } if (ret == 0) ret = dio->page_errors; if (ret == 0) ret = dio->io_error; if (ret == 0) ret = transferred; if (dio->end_io) { int err; // XXX: ki_pos?? err = dio->end_io(dio->iocb, offset, ret, dio->private); if (err) ret = err; } if (!(dio->flags & DIO_SKIP_DIO_COUNT)) inode_dio_end(dio->inode); if (is_async) { /* * generic_write_sync expects ki_pos to have been updated * already, but the submission path only does this for * synchronous I/O. */ dio->iocb->ki_pos += transferred; if (dio->op == REQ_OP_WRITE) ret = generic_write_sync(dio->iocb, transferred); dio->iocb->ki_complete(dio->iocb, ret, 0); } kmem_cache_free(dio_cache, dio); return ret; }


christoph hellwigchristoph hellwig11745.88%847.06%
zach brownzach brown6425.10%211.76%
stephen lordstephen lord3112.16%15.88%
al viroal viro176.67%15.88%
jens axboejens axboe124.71%15.88%
jan karajan kara62.35%15.88%
michael christiemichael christie51.96%15.88%
edward shishkinedward shishkin20.78%15.88%
andi kleenandi kleen10.39%15.88%

static void dio_aio_complete_work(struct work_struct *work) { struct dio *dio = container_of(work, struct dio, complete_work); dio_complete(dio, 0, true); }


christoph hellwigchristoph hellwig35100.00%1100.00%

static int dio_bio_complete(struct dio *dio, struct bio *bio); /* * Asynchronous IO callback. */
static void dio_bio_end_aio(struct bio *bio) { 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, 0, true); } } }


zach brownzach brown6849.28%450.00%
christoph hellwigchristoph hellwig4230.43%225.00%
andrew mortonandrew morton2719.57%112.50%
neil brownneil brown10.72%112.50%

/* * 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) { 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); }


andrew mortonandrew morton7292.31%457.14%
zach brownzach brown56.41%228.57%
neil brownneil brown11.28%114.29%

/** * 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); else dio_bio_end_io(bio); }


josef bacikjosef bacik39100.00%1100.00%

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_RECLAIM 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; bio_set_op_attrs(bio, dio->op, dio->op_flags); 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; }


andrew mortonandrew morton7168.93%220.00%
michael christiemichael christie1312.62%220.00%
andi kleenandi kleen98.74%220.00%
josef bacikjosef bacik65.83%110.00%
kent overstreetkent overstreet21.94%110.00%
david dillowdavid dillow10.97%110.00%
mel gormanmel gorman10.97%110.00%

/* * 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->op == REQ_OP_READ && dio->should_dirty) bio_set_pages_dirty(bio); dio->bio_bdev = bio->bi_bdev; if (sdio->submit_io) { sdio->submit_io(bio, dio->inode, sdio->logical_offset_in_bio); dio->bio_cookie = BLK_QC_T_NONE; } else dio->bio_cookie = submit_bio(bio); sdio->bio = NULL; sdio->boundary = 0; sdio->logical_offset_in_bio = 0; }


andrew mortonandrew morton6141.50%430.77%
josef bacikjosef bacik2416.33%17.69%
zach brownzach brown2315.65%215.38%
jens axboejens axboe2013.61%215.38%
andi kleenandi kleen138.84%215.38%
ming leiming lei42.72%17.69%
michael christiemichael christie21.36%17.69%

/* * 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) put_page(dio->pages[sdio->head++]); }


andrew mortonandrew morton1845.00%120.00%
al viroal viro1332.50%120.00%
andi kleenandi kleen820.00%240.00%
kirill a. shutemovkirill a. shutemov12.50%120.00%

/* * 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); if (!(dio->iocb->ki_flags & IOCB_HIPRI) || !blk_mq_poll(bdev_get_queue(dio->bio_bdev), dio->bio_cookie)) 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; }


andrew mortonandrew morton10467.10%444.44%
zach brownzach brown2314.84%222.22%
jens axboejens axboe1710.97%222.22%
christoph hellwigchristoph hellwig117.10%111.11%

/* * Process one completed BIO. No locks are held. */
static int dio_bio_complete(struct dio *dio, struct bio *bio) { struct bio_vec *bvec; unsigned i; int err; if (bio->bi_error) dio->io_error = -EIO; if (dio->is_async && dio->op == REQ_OP_READ && dio->should_dirty) { err = bio->bi_error; bio_check_pages_dirty(bio); /* transfers ownership */ } else { bio_for_each_segment_all(bvec, bio, i) { struct page *page = bvec->bv_page; if (dio->op == REQ_OP_READ && !PageCompound(page) && dio->should_dirty) set_page_dirty_lock(page); put_page(page); } err = bio->bi_error; bio_put(bio); } return err; }


andrew mortonandrew morton7858.21%325.00%
sasha levinsasha levin1611.94%18.33%
kent overstreetkent overstreet118.21%18.33%
ming leiming lei85.97%18.33%
kenneth w. chenkenneth w. chen75.22%216.67%
mike krinkinmike krinkin64.48%18.33%
michael christiemichael christie42.99%18.33%
christoph hellwigchristoph hellwig32.24%18.33%
kirill a. shutemovkirill a. shutemov10.75%18.33%

/* * 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); }


andrew mortonandrew morton2661.90%133.33%
zach brownzach brown1638.10%266.67%

/* * 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; }


andrew mortonandrew morton10793.04%360.00%
andi kleenandi kleen86.96%240.00%

/* * 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. */
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; }


christoph hellwigchristoph hellwig6288.57%150.00%
olof johanssonolof johansson811.43%150.00%

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; }


christoph hellwigchristoph hellwig53100.00%1100.00%

/* * 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 that could fill holes 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->op == REQ_OP_WRITE; if (dio->flags & DIO_SKIP_HOLES) { if (fs_startblk <= ((i_size_read(dio->inode) - 1) >> i_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; }


andrew mortonandrew morton10850.00%531.25%
andi kleenandi kleen2612.04%212.50%
nathan scottnathan scott2511.57%212.50%
christoph hellwigchristoph hellwig219.72%212.50%
linus torvaldslinus torvalds125.56%16.25%
tao matao ma125.56%16.25%
eryu guaneryu guan83.70%16.25%
michael christiemichael christie31.39%16.25%
badari pulavartybadari pulavarty10.46%16.25%

/* * 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_MAX_PAGES); BUG_ON(nr_pages <= 0); dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages); sdio->boundary = 0; out: return ret; }


andrew mortonandrew morton8580.95%660.00%
andi kleenandi kleen1918.10%330.00%
kent overstreetkent overstreet10.95%110.00%

/* * 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--; get_page(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; }


andrew mortonandrew morton7571.43%342.86%
andi kleenandi kleen1615.24%228.57%
badari pulavartybadari pulavarty1312.38%114.29%
kirill a. shutemovkirill a. shutemov10.95%114.29%

/* * 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; }


andrew mortonandrew morton11366.08%330.00%
andi kleenandi kleen3419.88%330.00%
josef bacikjosef bacik2011.70%110.00%
kent overstreetkent overstreet21.17%110.00%
jeff moyerjeff moyer10.58%110.00%
namhyung kimnamhyung kim10.58%110.00%

/* * 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->op == REQ_OP_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); put_page(sdio->cur_page); sdio->cur_page = NULL; if (ret) return ret; } get_page(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)