fs/ext4/page-io.c

   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/aio.h>
  22 #include <linux/uio.h>
  23 #include <linux/bio.h>
  24 #include <linux/workqueue.h>
  25 #include <linux/kernel.h>
  26 #include <linux/slab.h>
  27 #include <linux/mm.h>
  28 #include <linux/ratelimit.h>
  29
  30 #include "ext4_jbd2.h"
  31 #include "xattr.h"
  32 #include "acl.h"
  33
  34 static struct kmem_cache *io_end_cachep;
  35
  36 int __init ext4_init_pageio(void)
  37 {
  38         io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
  39         if (io_end_cachep == NULL)
  40                 return -ENOMEM;
  41         return 0;
  42 }
  43
  44 void ext4_exit_pageio(void)
  45 {
  46         kmem_cache_destroy(io_end_cachep);
  47 }
  48
  49 /*
  50  * Print an buffer I/O error compatible with the fs/buffer.c.  This
  51  * provides compatibility with dmesg scrapers that look for a specific
  52  * buffer I/O error message.  We really need a unified error reporting
  53  * structure to userspace ala Digital Unix's uerf system, but it's
  54  * probably not going to happen in my lifetime, due to LKML politics...
  55  */
  56 static void buffer_io_error(struct buffer_head *bh)
  57 {
  58         char b[BDEVNAME_SIZE];
  59         printk_ratelimited(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
  60                         bdevname(bh->b_bdev, b),
  61                         (unsigned long long)bh->b_blocknr);
  62 }
  63
  64 static void ext4_finish_bio(struct bio *bio)
  65 {
  66         int i;
  67         int error = !test_bit(BIO_UPTODATE, &bio->bi_flags);
  68
  69         for (i = 0; i < bio->bi_vcnt; i++) {
  70                 struct bio_vec *bvec = &bio->bi_io_vec[i];
  71                 struct page *page = bvec->bv_page;
  72                 struct buffer_head *bh, *head;
  73                 unsigned bio_start = bvec->bv_offset;
  74                 unsigned bio_end = bio_start + bvec->bv_len;
  75                 unsigned under_io = 0;
  76                 unsigned long flags;
  77
  78                 if (!page)
  79                         continue;
  80
  81                 if (error) {
  82                         SetPageError(page);
  83                         set_bit(AS_EIO, &page->mapping->flags);
  84                 }
  85                 bh = head = page_buffers(page);
  86                 /*
  87                  * We check all buffers in the page under BH_Uptodate_Lock
  88                  * to avoid races with other end io clearing async_write flags
  89                  */
  90                 local_irq_save(flags);
  91                 bit_spin_lock(BH_Uptodate_Lock, &head->b_state);
  92                 do {
  93                         if (bh_offset(bh) < bio_start ||
  94                             bh_offset(bh) + bh->b_size > bio_end) {
  95                                 if (buffer_async_write(bh))
  96                                         under_io++;
  97                                 continue;
  98                         }
  99                         clear_buffer_async_write(bh);
 100                         if (error)
 101                                 buffer_io_error(bh);
 102                 } while ((bh = bh->b_this_page) != head);
 103                 bit_spin_unlock(BH_Uptodate_Lock, &head->b_state);
 104                 local_irq_restore(flags);
 105                 if (!under_io)
 106                         end_page_writeback(page);
 107         }
 108 }
 109
 110 static void ext4_release_io_end(ext4_io_end_t *io_end)
 111 {
 112         struct bio *bio, *next_bio;
 113
 114         BUG_ON(!list_empty(&io_end->list));
 115         BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
 116         WARN_ON(io_end->handle);
 117
 118         if (atomic_dec_and_test(&EXT4_I(io_end->inode)->i_ioend_count))
 119                 wake_up_all(ext4_ioend_wq(io_end->inode));
 120
 121         for (bio = io_end->bio; bio; bio = next_bio) {
 122                 next_bio = bio->bi_private;
 123                 ext4_finish_bio(bio);
 124                 bio_put(bio);
 125         }
 126         kmem_cache_free(io_end_cachep, io_end);
 127 }
 128
 129 static void ext4_clear_io_unwritten_flag(ext4_io_end_t *io_end)
 130 {
 131         struct inode *inode = io_end->inode;
 132
 133         io_end->flag &= ~EXT4_IO_END_UNWRITTEN;
 134         /* Wake up anyone waiting on unwritten extent conversion */
 135         if (atomic_dec_and_test(&EXT4_I(inode)->i_unwritten))
 136                 wake_up_all(ext4_ioend_wq(inode));
 137 }
 138
 139 /*
 140  * Check a range of space and convert unwritten extents to written. Note that
 141  * we are protected from truncate touching same part of extent tree by the
 142  * fact that truncate code waits for all DIO to finish (thus exclusion from
 143  * direct IO is achieved) and also waits for PageWriteback bits. Thus we
 144  * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
 145  * completed (happens from ext4_free_ioend()).
 146  */
 147 static int ext4_end_io(ext4_io_end_t *io)
 148 {
 149         struct inode *inode = io->inode;
 150         loff_t offset = io->offset;
 151         ssize_t size = io->size;
 152         handle_t *handle = io->handle;
 153         int ret = 0;
 154
 155         ext4_debug("ext4_end_io_nolock: io 0x%p from inode %lu,list->next 0x%p,"
 156                    "list->prev 0x%p\n",
 157                    io, inode->i_ino, io->list.next, io->list.prev);
 158
 159         io->handle = NULL;      /* Following call will use up the handle */
 160         ret = ext4_convert_unwritten_extents(handle, inode, offset, size);
 161         if (ret < 0) {
 162                 ext4_msg(inode->i_sb, KERN_EMERG,
 163                          "failed to convert unwritten extents to written "
 164                          "extents -- potential data loss!  "
 165                          "(inode %lu, offset %llu, size %zd, error %d)",
 166                          inode->i_ino, offset, size, ret);
 167         }
 168         ext4_clear_io_unwritten_flag(io);
 169         ext4_release_io_end(io);
 170         return ret;
 171 }
 172
 173 static void dump_completed_IO(struct inode *inode, struct list_head *head)
 174 {
 175 #ifdef  EXT4FS_DEBUG
 176         struct list_head *cur, *before, *after;
 177         ext4_io_end_t *io, *io0, *io1;
 178
 179         if (list_empty(head))
 180                 return;
 181
 182         ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
 183         list_for_each_entry(io, head, list) {
 184                 cur = &io->list;
 185                 before = cur->prev;
 186                 io0 = container_of(before, ext4_io_end_t, list);
 187                 after = cur->next;
 188                 io1 = container_of(after, ext4_io_end_t, list);
 189
 190                 ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
 191                             io, inode->i_ino, io0, io1);
 192         }
 193 #endif
 194 }
 195
 196 /* Add the io_end to per-inode completed end_io list. */
 197 static void ext4_add_complete_io(ext4_io_end_t *io_end)
 198 {
 199         struct ext4_inode_info *ei = EXT4_I(io_end->inode);
 200         struct workqueue_struct *wq;
 201         unsigned long flags;
 202
 203         /* Only reserved conversions from writeback should enter here */
 204         WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
 205         WARN_ON(!io_end->handle);
 206         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 207         wq = EXT4_SB(io_end->inode->i_sb)->rsv_conversion_wq;
 208         if (list_empty(&ei->i_rsv_conversion_list))
 209                 queue_work(wq, &ei->i_rsv_conversion_work);
 210         list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
 211         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 212 }
 213
 214 static int ext4_do_flush_completed_IO(struct inode *inode,
 215                                       struct list_head *head)
 216 {
 217         ext4_io_end_t *io;
 218         struct list_head unwritten;
 219         unsigned long flags;
 220         struct ext4_inode_info *ei = EXT4_I(inode);
 221         int err, ret = 0;
 222
 223         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 224         dump_completed_IO(inode, head);
 225         list_replace_init(head, &unwritten);
 226         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 227
 228         while (!list_empty(&unwritten)) {
 229                 io = list_entry(unwritten.next, ext4_io_end_t, list);
 230                 BUG_ON(!(io->flag & EXT4_IO_END_UNWRITTEN));
 231                 list_del_init(&io->list);
 232
 233                 err = ext4_end_io(io);
 234                 if (unlikely(!ret && err))
 235                         ret = err;
 236         }
 237         return ret;
 238 }
 239
 240 /*
 241  * work on completed IO, to convert unwritten extents to extents
 242  */
 243 void ext4_end_io_rsv_work(struct work_struct *work)
 244 {
 245         struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
 246                                                   i_rsv_conversion_work);
 247         ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
 248 }
 249
 250 ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
 251 {
 252         ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
 253         if (io) {
 254                 atomic_inc(&EXT4_I(inode)->i_ioend_count);
 255                 io->inode = inode;
 256                 INIT_LIST_HEAD(&io->list);
 257                 atomic_set(&io->count, 1);
 258         }
 259         return io;
 260 }
 261
 262 void ext4_put_io_end_defer(ext4_io_end_t *io_end)
 263 {
 264         if (atomic_dec_and_test(&io_end->count)) {
 265                 if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) || !io_end->size) {
 266                         ext4_release_io_end(io_end);
 267                         return;
 268                 }
 269                 ext4_add_complete_io(io_end);
 270         }
 271 }
 272
 273 int ext4_put_io_end(ext4_io_end_t *io_end)
 274 {
 275         int err = 0;
 276
 277         if (atomic_dec_and_test(&io_end->count)) {
 278                 if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
 279                         err = ext4_convert_unwritten_extents(io_end->handle,
 280                                                 io_end->inode, io_end->offset,
 281                                                 io_end->size);
 282                         io_end->handle = NULL;
 283                         ext4_clear_io_unwritten_flag(io_end);
 284                 }
 285                 ext4_release_io_end(io_end);
 286         }
 287         return err;
 288 }
 289
 290 ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
 291 {
 292         atomic_inc(&io_end->count);
 293         return io_end;
 294 }
 295
 296 /* BIO completion function for page writeback */
 297 static void ext4_end_bio(struct bio *bio, int error)
 298 {
 299         ext4_io_end_t *io_end = bio->bi_private;
 300         sector_t bi_sector = bio->bi_sector;
 301
 302         BUG_ON(!io_end);
 303         bio->bi_end_io = NULL;
 304         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 305                 error = 0;
 306
 307         if (error) {
 308                 struct inode *inode = io_end->inode;
 309
 310                 ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
 311                              "(offset %llu size %ld starting block %llu)",
 312                              error, inode->i_ino,
 313                              (unsigned long long) io_end->offset,
 314                              (long) io_end->size,
 315                              (unsigned long long)
 316                              bi_sector >> (inode->i_blkbits - 9));
 317                 mapping_set_error(inode->i_mapping, error);
 318         }
 319
 320         if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
 321                 /*
 322                  * Link bio into list hanging from io_end. We have to do it
 323                  * atomically as bio completions can be racing against each
 324                  * other.
 325                  */
 326                 bio->bi_private = xchg(&io_end->bio, bio);
 327                 ext4_put_io_end_defer(io_end);
 328         } else {
 329                 /*
 330                  * Drop io_end reference early. Inode can get freed once
 331                  * we finish the bio.
 332                  */
 333                 ext4_put_io_end_defer(io_end);
 334                 ext4_finish_bio(bio);
 335                 bio_put(bio);
 336         }
 337 }
 338
 339 void ext4_io_submit(struct ext4_io_submit *io)
 340 {
 341         struct bio *bio = io->io_bio;
 342
 343         if (bio) {
 344                 bio_get(io->io_bio);
 345                 submit_bio(io->io_op, io->io_bio);
 346                 BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
 347                 bio_put(io->io_bio);
 348         }
 349         io->io_bio = NULL;
 350 }
 351
 352 void ext4_io_submit_init(struct ext4_io_submit *io,
 353                          struct writeback_control *wbc)
 354 {
 355         io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
 356         io->io_bio = NULL;
 357         io->io_end = NULL;
 358 }
 359
 360 static int io_submit_init_bio(struct ext4_io_submit *io,
 361                               struct buffer_head *bh)
 362 {
 363         int nvecs = bio_get_nr_vecs(bh->b_bdev);
 364         struct bio *bio;
 365
 366         bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
 367         if (!bio)
 368                 return -ENOMEM;
 369         bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 370         bio->bi_bdev = bh->b_bdev;
 371         bio->bi_end_io = ext4_end_bio;
 372         bio->bi_private = ext4_get_io_end(io->io_end);
 373         io->io_bio = bio;
 374         io->io_next_block = bh->b_blocknr;
 375         return 0;
 376 }
 377
 378 static int io_submit_add_bh(struct ext4_io_submit *io,
 379                             struct inode *inode,
 380                             struct buffer_head *bh)
 381 {
 382         int ret;
 383
 384         if (io->io_bio && bh->b_blocknr != io->io_next_block) {
 385 submit_and_retry:
 386                 ext4_io_submit(io);
 387         }
 388         if (io->io_bio == NULL) {
 389                 ret = io_submit_init_bio(io, bh);
 390                 if (ret)
 391                         return ret;
 392         }
 393         ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
 394         if (ret != bh->b_size)
 395                 goto submit_and_retry;
 396         io->io_next_block++;
 397         return 0;
 398 }
 399
 400 int ext4_bio_write_page(struct ext4_io_submit *io,
 401                         struct page *page,
 402                         int len,
 403                         struct writeback_control *wbc,
 404                         bool keep_towrite)
 405 {
 406         struct inode *inode = page->mapping->host;
 407         unsigned block_start, blocksize;
 408         struct buffer_head *bh, *head;
 409         int ret = 0;
 410         int nr_submitted = 0;
 411
 412         blocksize = 1 << inode->i_blkbits;
 413
 414         BUG_ON(!PageLocked(page));
 415         BUG_ON(PageWriteback(page));
 416
 417         if (keep_towrite)
 418                 set_page_writeback_keepwrite(page);
 419         else
 420                 set_page_writeback(page);
 421         ClearPageError(page);
 422
 423         /*
 424          * Comments copied from block_write_full_page_endio:
 425          *
 426          * The page straddles i_size.  It must be zeroed out on each and every
 427          * writepage invocation because it may be mmapped.  "A file is mapped
 428          * in multiples of the page size.  For a file that is not a multiple of
 429          * the page size, the remaining memory is zeroed when mapped, and
 430          * writes to that region are not written out to the file."
 431          */
 432         if (len < PAGE_CACHE_SIZE)
 433                 zero_user_segment(page, len, PAGE_CACHE_SIZE);
 434         /*
 435          * In the first loop we prepare and mark buffers to submit. We have to
 436          * mark all buffers in the page before submitting so that
 437          * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
 438          * on the first buffer finishes and we are still working on submitting
 439          * the second buffer.
 440          */
 441         bh = head = page_buffers(page);
 442         do {
 443                 block_start = bh_offset(bh);
 444                 if (block_start >= len) {
 445                         clear_buffer_dirty(bh);
 446                         set_buffer_uptodate(bh);
 447                         continue;
 448                 }
 449                 if (!buffer_dirty(bh) || buffer_delay(bh) ||
 450                     !buffer_mapped(bh) || buffer_unwritten(bh)) {
 451                         /* A hole? We can safely clear the dirty bit */
 452                         if (!buffer_mapped(bh))
 453                                 clear_buffer_dirty(bh);
 454                         if (io->io_bio)
 455                                 ext4_io_submit(io);
 456                         continue;
 457                 }
 458                 if (buffer_new(bh)) {
 459                         clear_buffer_new(bh);
 460                         unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
 461                 }
 462                 set_buffer_async_write(bh);
 463         } while ((bh = bh->b_this_page) != head);
 464
 465         /* Now submit buffers to write */
 466         bh = head = page_buffers(page);
 467         do {
 468                 if (!buffer_async_write(bh))
 469                         continue;
 470                 ret = io_submit_add_bh(io, inode, bh);
 471                 if (ret) {
 472                         /*
 473                          * We only get here on ENOMEM.  Not much else
 474                          * we can do but mark the page as dirty, and
 475                          * better luck next time.
 476                          */
 477                         redirty_page_for_writepage(wbc, page);
 478                         break;
 479                 }
 480                 nr_submitted++;
 481                 clear_buffer_dirty(bh);
 482         } while ((bh = bh->b_this_page) != head);
 483
 484         /* Error stopped previous loop? Clean up buffers... */
 485         if (ret) {
 486                 do {
 487                         clear_buffer_async_write(bh);
 488                         bh = bh->b_this_page;
 489                 } while (bh != head);
 490         }
 491         unlock_page(page);
 492         /* Nothing submitted - we have to end page writeback */
 493         if (!nr_submitted)
 494                 end_page_writeback(page);
 495         return ret;
 496 }