linux/fs/ext4/page-io.c
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   1/*
   2 * linux/fs/ext4/page-io.c
   3 *
   4 * This contains the new page_io functions for ext4
   5 *
   6 * Written by Theodore Ts'o, 2010.
   7 */
   8
   9#include <linux/fs.h>
  10#include <linux/time.h>
  11#include <linux/jbd2.h>
  12#include <linux/highuid.h>
  13#include <linux/pagemap.h>
  14#include <linux/quotaops.h>
  15#include <linux/string.h>
  16#include <linux/buffer_head.h>
  17#include <linux/writeback.h>
  18#include <linux/pagevec.h>
  19#include <linux/mpage.h>
  20#include <linux/namei.h>
  21#include <linux/uio.h>
  22#include <linux/bio.h>
  23#include <linux/workqueue.h>
  24#include <linux/kernel.h>
  25#include <linux/slab.h>
  26
  27#include "ext4_jbd2.h"
  28#include "xattr.h"
  29#include "acl.h"
  30#include "ext4_extents.h"
  31
  32static struct kmem_cache *io_page_cachep, *io_end_cachep;
  33
  34int __init ext4_init_pageio(void)
  35{
  36        io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT);
  37        if (io_page_cachep == NULL)
  38                return -ENOMEM;
  39        io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
  40        if (io_end_cachep == NULL) {
  41                kmem_cache_destroy(io_page_cachep);
  42                return -ENOMEM;
  43        }
  44        return 0;
  45}
  46
  47void ext4_exit_pageio(void)
  48{
  49        kmem_cache_destroy(io_end_cachep);
  50        kmem_cache_destroy(io_page_cachep);
  51}
  52
  53void ext4_ioend_wait(struct inode *inode)
  54{
  55        wait_queue_head_t *wq = ext4_ioend_wq(inode);
  56
  57        wait_event(*wq, (atomic_read(&EXT4_I(inode)->i_ioend_count) == 0));
  58}
  59
  60static void put_io_page(struct ext4_io_page *io_page)
  61{
  62        if (atomic_dec_and_test(&io_page->p_count)) {
  63                end_page_writeback(io_page->p_page);
  64                put_page(io_page->p_page);
  65                kmem_cache_free(io_page_cachep, io_page);
  66        }
  67}
  68
  69void ext4_free_io_end(ext4_io_end_t *io)
  70{
  71        int i;
  72
  73        BUG_ON(!io);
  74        if (io->page)
  75                put_page(io->page);
  76        for (i = 0; i < io->num_io_pages; i++)
  77                put_io_page(io->pages[i]);
  78        io->num_io_pages = 0;
  79        if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count))
  80                wake_up_all(ext4_ioend_wq(io->inode));
  81        kmem_cache_free(io_end_cachep, io);
  82}
  83
  84/*
  85 * check a range of space and convert unwritten extents to written.
  86 *
  87 * Called with inode->i_mutex; we depend on this when we manipulate
  88 * io->flag, since we could otherwise race with ext4_flush_completed_IO()
  89 */
  90int ext4_end_io_nolock(ext4_io_end_t *io)
  91{
  92        struct inode *inode = io->inode;
  93        loff_t offset = io->offset;
  94        ssize_t size = io->size;
  95        int ret = 0;
  96
  97        ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
  98                   "list->prev 0x%p\n",
  99                   io, inode->i_ino, io->list.next, io->list.prev);
 100
 101        ret = ext4_convert_unwritten_extents(inode, offset, size);
 102        if (ret < 0) {
 103                ext4_msg(inode->i_sb, KERN_EMERG,
 104                         "failed to convert unwritten extents to written "
 105                         "extents -- potential data loss!  "
 106                         "(inode %lu, offset %llu, size %zd, error %d)",
 107                         inode->i_ino, offset, size, ret);
 108        }
 109
 110        if (io->iocb)
 111                aio_complete(io->iocb, io->result, 0);
 112
 113        if (io->flag & EXT4_IO_END_DIRECT)
 114                inode_dio_done(inode);
 115        /* Wake up anyone waiting on unwritten extent conversion */
 116        if (atomic_dec_and_test(&EXT4_I(inode)->i_aiodio_unwritten))
 117                wake_up_all(ext4_ioend_wq(io->inode));
 118        return ret;
 119}
 120
 121/*
 122 * work on completed aio dio IO, to convert unwritten extents to extents
 123 */
 124static void ext4_end_io_work(struct work_struct *work)
 125{
 126        ext4_io_end_t           *io = container_of(work, ext4_io_end_t, work);
 127        struct inode            *inode = io->inode;
 128        struct ext4_inode_info  *ei = EXT4_I(inode);
 129        unsigned long           flags;
 130
 131        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 132        if (io->flag & EXT4_IO_END_IN_FSYNC)
 133                goto requeue;
 134        if (list_empty(&io->list)) {
 135                spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 136                goto free;
 137        }
 138
 139        if (!mutex_trylock(&inode->i_mutex)) {
 140                bool was_queued;
 141requeue:
 142                was_queued = !!(io->flag & EXT4_IO_END_QUEUED);
 143                io->flag |= EXT4_IO_END_QUEUED;
 144                spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 145                /*
 146                 * Requeue the work instead of waiting so that the work
 147                 * items queued after this can be processed.
 148                 */
 149                queue_work(EXT4_SB(inode->i_sb)->dio_unwritten_wq, &io->work);
 150                /*
 151                 * To prevent the ext4-dio-unwritten thread from keeping
 152                 * requeueing end_io requests and occupying cpu for too long,
 153                 * yield the cpu if it sees an end_io request that has already
 154                 * been requeued.
 155                 */
 156                if (was_queued)
 157                        yield();
 158                return;
 159        }
 160        list_del_init(&io->list);
 161        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 162        (void) ext4_end_io_nolock(io);
 163        mutex_unlock(&inode->i_mutex);
 164free:
 165        ext4_free_io_end(io);
 166}
 167
 168ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
 169{
 170        ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
 171        if (io) {
 172                atomic_inc(&EXT4_I(inode)->i_ioend_count);
 173                io->inode = inode;
 174                INIT_WORK(&io->work, ext4_end_io_work);
 175                INIT_LIST_HEAD(&io->list);
 176        }
 177        return io;
 178}
 179
 180/*
 181 * Print an buffer I/O error compatible with the fs/buffer.c.  This
 182 * provides compatibility with dmesg scrapers that look for a specific
 183 * buffer I/O error message.  We really need a unified error reporting
 184 * structure to userspace ala Digital Unix's uerf system, but it's
 185 * probably not going to happen in my lifetime, due to LKML politics...
 186 */
 187static void buffer_io_error(struct buffer_head *bh)
 188{
 189        char b[BDEVNAME_SIZE];
 190        printk(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
 191                        bdevname(bh->b_bdev, b),
 192                        (unsigned long long)bh->b_blocknr);
 193}
 194
 195static void ext4_end_bio(struct bio *bio, int error)
 196{
 197        ext4_io_end_t *io_end = bio->bi_private;
 198        struct workqueue_struct *wq;
 199        struct inode *inode;
 200        unsigned long flags;
 201        int i;
 202        sector_t bi_sector = bio->bi_sector;
 203
 204        BUG_ON(!io_end);
 205        bio->bi_private = NULL;
 206        bio->bi_end_io = NULL;
 207        if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 208                error = 0;
 209        bio_put(bio);
 210
 211        for (i = 0; i < io_end->num_io_pages; i++) {
 212                struct page *page = io_end->pages[i]->p_page;
 213                struct buffer_head *bh, *head;
 214                loff_t offset;
 215                loff_t io_end_offset;
 216
 217                if (error) {
 218                        SetPageError(page);
 219                        set_bit(AS_EIO, &page->mapping->flags);
 220                        head = page_buffers(page);
 221                        BUG_ON(!head);
 222
 223                        io_end_offset = io_end->offset + io_end->size;
 224
 225                        offset = (sector_t) page->index << PAGE_CACHE_SHIFT;
 226                        bh = head;
 227                        do {
 228                                if ((offset >= io_end->offset) &&
 229                                    (offset+bh->b_size <= io_end_offset))
 230                                        buffer_io_error(bh);
 231
 232                                offset += bh->b_size;
 233                                bh = bh->b_this_page;
 234                        } while (bh != head);
 235                }
 236
 237                put_io_page(io_end->pages[i]);
 238        }
 239        io_end->num_io_pages = 0;
 240        inode = io_end->inode;
 241
 242        if (error) {
 243                io_end->flag |= EXT4_IO_END_ERROR;
 244                ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
 245                             "(offset %llu size %ld starting block %llu)",
 246                             inode->i_ino,
 247                             (unsigned long long) io_end->offset,
 248                             (long) io_end->size,
 249                             (unsigned long long)
 250                             bi_sector >> (inode->i_blkbits - 9));
 251        }
 252
 253        if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
 254                ext4_free_io_end(io_end);
 255                return;
 256        }
 257
 258        /* Add the io_end to per-inode completed io list*/
 259        spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
 260        list_add_tail(&io_end->list, &EXT4_I(inode)->i_completed_io_list);
 261        spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);
 262
 263        wq = EXT4_SB(inode->i_sb)->dio_unwritten_wq;
 264        /* queue the work to convert unwritten extents to written */
 265        queue_work(wq, &io_end->work);
 266}
 267
 268void ext4_io_submit(struct ext4_io_submit *io)
 269{
 270        struct bio *bio = io->io_bio;
 271
 272        if (bio) {
 273                bio_get(io->io_bio);
 274                submit_bio(io->io_op, io->io_bio);
 275                BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
 276                bio_put(io->io_bio);
 277        }
 278        io->io_bio = NULL;
 279        io->io_op = 0;
 280        io->io_end = NULL;
 281}
 282
 283static int io_submit_init(struct ext4_io_submit *io,
 284                          struct inode *inode,
 285                          struct writeback_control *wbc,
 286                          struct buffer_head *bh)
 287{
 288        ext4_io_end_t *io_end;
 289        struct page *page = bh->b_page;
 290        int nvecs = bio_get_nr_vecs(bh->b_bdev);
 291        struct bio *bio;
 292
 293        io_end = ext4_init_io_end(inode, GFP_NOFS);
 294        if (!io_end)
 295                return -ENOMEM;
 296        bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
 297        bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 298        bio->bi_bdev = bh->b_bdev;
 299        bio->bi_private = io->io_end = io_end;
 300        bio->bi_end_io = ext4_end_bio;
 301
 302        io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);
 303
 304        io->io_bio = bio;
 305        io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
 306        io->io_next_block = bh->b_blocknr;
 307        return 0;
 308}
 309
 310static int io_submit_add_bh(struct ext4_io_submit *io,
 311                            struct ext4_io_page *io_page,
 312                            struct inode *inode,
 313                            struct writeback_control *wbc,
 314                            struct buffer_head *bh)
 315{
 316        ext4_io_end_t *io_end;
 317        int ret;
 318
 319        if (buffer_new(bh)) {
 320                clear_buffer_new(bh);
 321                unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
 322        }
 323
 324        if (!buffer_mapped(bh) || buffer_delay(bh)) {
 325                if (!buffer_mapped(bh))
 326                        clear_buffer_dirty(bh);
 327                if (io->io_bio)
 328                        ext4_io_submit(io);
 329                return 0;
 330        }
 331
 332        if (io->io_bio && bh->b_blocknr != io->io_next_block) {
 333submit_and_retry:
 334                ext4_io_submit(io);
 335        }
 336        if (io->io_bio == NULL) {
 337                ret = io_submit_init(io, inode, wbc, bh);
 338                if (ret)
 339                        return ret;
 340        }
 341        io_end = io->io_end;
 342        if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
 343            (io_end->pages[io_end->num_io_pages-1] != io_page))
 344                goto submit_and_retry;
 345        if (buffer_uninit(bh))
 346                ext4_set_io_unwritten_flag(inode, io_end);
 347        io->io_end->size += bh->b_size;
 348        io->io_next_block++;
 349        ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
 350        if (ret != bh->b_size)
 351                goto submit_and_retry;
 352        if ((io_end->num_io_pages == 0) ||
 353            (io_end->pages[io_end->num_io_pages-1] != io_page)) {
 354                io_end->pages[io_end->num_io_pages++] = io_page;
 355                atomic_inc(&io_page->p_count);
 356        }
 357        return 0;
 358}
 359
 360int ext4_bio_write_page(struct ext4_io_submit *io,
 361                        struct page *page,
 362                        int len,
 363                        struct writeback_control *wbc)
 364{
 365        struct inode *inode = page->mapping->host;
 366        unsigned block_start, block_end, blocksize;
 367        struct ext4_io_page *io_page;
 368        struct buffer_head *bh, *head;
 369        int ret = 0;
 370
 371        blocksize = 1 << inode->i_blkbits;
 372
 373        BUG_ON(!PageLocked(page));
 374        BUG_ON(PageWriteback(page));
 375
 376        io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
 377        if (!io_page) {
 378                set_page_dirty(page);
 379                unlock_page(page);
 380                return -ENOMEM;
 381        }
 382        io_page->p_page = page;
 383        atomic_set(&io_page->p_count, 1);
 384        get_page(page);
 385        set_page_writeback(page);
 386        ClearPageError(page);
 387
 388        for (bh = head = page_buffers(page), block_start = 0;
 389             bh != head || !block_start;
 390             block_start = block_end, bh = bh->b_this_page) {
 391
 392                block_end = block_start + blocksize;
 393                if (block_start >= len) {
 394                        /*
 395                         * Comments copied from block_write_full_page_endio:
 396                         *
 397                         * The page straddles i_size.  It must be zeroed out on
 398                         * each and every writepage invocation because it may
 399                         * be mmapped.  "A file is mapped in multiples of the
 400                         * page size.  For a file that is not a multiple of
 401                         * the  page size, the remaining memory is zeroed when
 402                         * mapped, and writes to that region are not written
 403                         * out to the file."
 404                         */
 405                        zero_user_segment(page, block_start, block_end);
 406                        clear_buffer_dirty(bh);
 407                        set_buffer_uptodate(bh);
 408                        continue;
 409                }
 410                clear_buffer_dirty(bh);
 411                ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
 412                if (ret) {
 413                        /*
 414                         * We only get here on ENOMEM.  Not much else
 415                         * we can do but mark the page as dirty, and
 416                         * better luck next time.
 417                         */
 418                        set_page_dirty(page);
 419                        break;
 420                }
 421        }
 422        unlock_page(page);
 423        /*
 424         * If the page was truncated before we could do the writeback,
 425         * or we had a memory allocation error while trying to write
 426         * the first buffer head, we won't have submitted any pages for
 427         * I/O.  In that case we need to make sure we've cleared the
 428         * PageWriteback bit from the page to prevent the system from
 429         * wedging later on.
 430         */
 431        put_io_page(io_page);
 432        return ret;
 433}
 434
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