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/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
  32 static struct kmem_cache *io_page_cachep, *io_end_cachep;
  33
  34 int __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
  47 void ext4_exit_pageio(void)
  48 {
  49         kmem_cache_destroy(io_end_cachep);
  50         kmem_cache_destroy(io_page_cachep);
  51 }
  52
  53 void 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
  60 static 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
  69 void 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  */
  90 int 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         /* Wake up anyone waiting on unwritten extent conversion */
 114         if (atomic_dec_and_test(&EXT4_I(inode)->i_aiodio_unwritten))
 115                 wake_up_all(ext4_ioend_wq(io->inode));
 116         return ret;
 117 }
 118
 119 /*
 120  * work on completed aio dio IO, to convert unwritten extents to extents
 121  */
 122 static void ext4_end_io_work(struct work_struct *work)
 123 {
 124         ext4_io_end_t           *io = container_of(work, ext4_io_end_t, work);
 125         struct inode            *inode = io->inode;
 126         struct ext4_inode_info  *ei = EXT4_I(inode);
 127         unsigned long           flags;
 128
 129         spin_lock_irqsave(&ei->i_completed_io_lock, flags);
 130         if (list_empty(&io->list)) {
 131                 spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 132                 goto free;
 133         }
 134
 135         if (!mutex_trylock(&inode->i_mutex)) {
 136                 spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 137                 /*
 138                  * Requeue the work instead of waiting so that the work
 139                  * items queued after this can be processed.
 140                  */
 141                 queue_work(EXT4_SB(inode->i_sb)->dio_unwritten_wq, &io->work);
 142                 /*
 143                  * To prevent the ext4-dio-unwritten thread from keeping
 144                  * requeueing end_io requests and occupying cpu for too long,
 145                  * yield the cpu if it sees an end_io request that has already
 146                  * been requeued.
 147                  */
 148                 if (io->flag & EXT4_IO_END_QUEUED)
 149                         yield();
 150                 io->flag |= EXT4_IO_END_QUEUED;
 151                 return;
 152         }
 153         list_del_init(&io->list);
 154         spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
 155         (void) ext4_end_io_nolock(io);
 156         mutex_unlock(&inode->i_mutex);
 157 free:
 158         ext4_free_io_end(io);
 159 }
 160
 161 ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
 162 {
 163         ext4_io_end_t *io = kmem_cache_zalloc(io_end_cachep, flags);
 164         if (io) {
 165                 atomic_inc(&EXT4_I(inode)->i_ioend_count);
 166                 io->inode = inode;
 167                 INIT_WORK(&io->work, ext4_end_io_work);
 168                 INIT_LIST_HEAD(&io->list);
 169         }
 170         return io;
 171 }
 172
 173 /*
 174  * Print an buffer I/O error compatible with the fs/buffer.c.  This
 175  * provides compatibility with dmesg scrapers that look for a specific
 176  * buffer I/O error message.  We really need a unified error reporting
 177  * structure to userspace ala Digital Unix's uerf system, but it's
 178  * probably not going to happen in my lifetime, due to LKML politics...
 179  */
 180 static void buffer_io_error(struct buffer_head *bh)
 181 {
 182         char b[BDEVNAME_SIZE];
 183         printk(KERN_ERR "Buffer I/O error on device %s, logical block %llu\n",
 184                         bdevname(bh->b_bdev, b),
 185                         (unsigned long long)bh->b_blocknr);
 186 }
 187
 188 static void ext4_end_bio(struct bio *bio, int error)
 189 {
 190         ext4_io_end_t *io_end = bio->bi_private;
 191         struct workqueue_struct *wq;
 192         struct inode *inode;
 193         unsigned long flags;
 194         int i;
 195         sector_t bi_sector = bio->bi_sector;
 196
 197         BUG_ON(!io_end);
 198         bio->bi_private = NULL;
 199         bio->bi_end_io = NULL;
 200         if (test_bit(BIO_UPTODATE, &bio->bi_flags))
 201                 error = 0;
 202         bio_put(bio);
 203
 204         for (i = 0; i < io_end->num_io_pages; i++) {
 205                 struct page *page = io_end->pages[i]->p_page;
 206                 struct buffer_head *bh, *head;
 207                 loff_t offset;
 208                 loff_t io_end_offset;
 209
 210                 if (error) {
 211                         SetPageError(page);
 212                         set_bit(AS_EIO, &page->mapping->flags);
 213                         head = page_buffers(page);
 214                         BUG_ON(!head);
 215
 216                         io_end_offset = io_end->offset + io_end->size;
 217
 218                         offset = (sector_t) page->index << PAGE_CACHE_SHIFT;
 219                         bh = head;
 220                         do {
 221                                 if ((offset >= io_end->offset) &&
 222                                     (offset+bh->b_size <= io_end_offset))
 223                                         buffer_io_error(bh);
 224
 225                                 offset += bh->b_size;
 226                                 bh = bh->b_this_page;
 227                         } while (bh != head);
 228                 }
 229
 230                 put_io_page(io_end->pages[i]);
 231         }
 232         io_end->num_io_pages = 0;
 233         inode = io_end->inode;
 234
 235         if (error) {
 236                 io_end->flag |= EXT4_IO_END_ERROR;
 237                 ext4_warning(inode->i_sb, "I/O error writing to inode %lu "
 238                              "(offset %llu size %ld starting block %llu)",
 239                              inode->i_ino,
 240                              (unsigned long long) io_end->offset,
 241                              (long) io_end->size,
 242                              (unsigned long long)
 243                              bi_sector >> (inode->i_blkbits - 9));
 244         }
 245
 246         if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
 247                 ext4_free_io_end(io_end);
 248                 return;
 249         }
 250
 251         /* Add the io_end to per-inode completed io list*/
 252         spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);
 253         list_add_tail(&io_end->list, &EXT4_I(inode)->i_completed_io_list);
 254         spin_unlock_irqrestore(&EXT4_I(inode)->i_completed_io_lock, flags);
 255
 256         wq = EXT4_SB(inode->i_sb)->dio_unwritten_wq;
 257         /* queue the work to convert unwritten extents to written */
 258         queue_work(wq, &io_end->work);
 259 }
 260
 261 void ext4_io_submit(struct ext4_io_submit *io)
 262 {
 263         struct bio *bio = io->io_bio;
 264
 265         if (bio) {
 266                 bio_get(io->io_bio);
 267                 submit_bio(io->io_op, io->io_bio);
 268                 BUG_ON(bio_flagged(io->io_bio, BIO_EOPNOTSUPP));
 269                 bio_put(io->io_bio);
 270         }
 271         io->io_bio = NULL;
 272         io->io_op = 0;
 273         io->io_end = NULL;
 274 }
 275
 276 static int io_submit_init(struct ext4_io_submit *io,
 277                           struct inode *inode,
 278                           struct writeback_control *wbc,
 279                           struct buffer_head *bh)
 280 {
 281         ext4_io_end_t *io_end;
 282         struct page *page = bh->b_page;
 283         int nvecs = bio_get_nr_vecs(bh->b_bdev);
 284         struct bio *bio;
 285
 286         io_end = ext4_init_io_end(inode, GFP_NOFS);
 287         if (!io_end)
 288                 return -ENOMEM;
 289         bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
 290         bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
 291         bio->bi_bdev = bh->b_bdev;
 292         bio->bi_private = io->io_end = io_end;
 293         bio->bi_end_io = ext4_end_bio;
 294
 295         io_end->offset = (page->index << PAGE_CACHE_SHIFT) + bh_offset(bh);
 296
 297         io->io_bio = bio;
 298         io->io_op = (wbc->sync_mode == WB_SYNC_ALL ?  WRITE_SYNC : WRITE);
 299         io->io_next_block = bh->b_blocknr;
 300         return 0;
 301 }
 302
 303 static int io_submit_add_bh(struct ext4_io_submit *io,
 304                             struct ext4_io_page *io_page,
 305                             struct inode *inode,
 306                             struct writeback_control *wbc,
 307                             struct buffer_head *bh)
 308 {
 309         ext4_io_end_t *io_end;
 310         int ret;
 311
 312         if (buffer_new(bh)) {
 313                 clear_buffer_new(bh);
 314                 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
 315         }
 316
 317         if (!buffer_mapped(bh) || buffer_delay(bh)) {
 318                 if (!buffer_mapped(bh))
 319                         clear_buffer_dirty(bh);
 320                 if (io->io_bio)
 321                         ext4_io_submit(io);
 322                 return 0;
 323         }
 324
 325         if (io->io_bio && bh->b_blocknr != io->io_next_block) {
 326 submit_and_retry:
 327                 ext4_io_submit(io);
 328         }
 329         if (io->io_bio == NULL) {
 330                 ret = io_submit_init(io, inode, wbc, bh);
 331                 if (ret)
 332                         return ret;
 333         }
 334         io_end = io->io_end;
 335         if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
 336             (io_end->pages[io_end->num_io_pages-1] != io_page))
 337                 goto submit_and_retry;
 338         if (buffer_uninit(bh))
 339                 ext4_set_io_unwritten_flag(inode, io_end);
 340         io->io_end->size += bh->b_size;
 341         io->io_next_block++;
 342         ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));
 343         if (ret != bh->b_size)
 344                 goto submit_and_retry;
 345         if ((io_end->num_io_pages == 0) ||
 346             (io_end->pages[io_end->num_io_pages-1] != io_page)) {
 347                 io_end->pages[io_end->num_io_pages++] = io_page;
 348                 atomic_inc(&io_page->p_count);
 349         }
 350         return 0;
 351 }
 352
 353 int ext4_bio_write_page(struct ext4_io_submit *io,
 354                         struct page *page,
 355                         int len,
 356                         struct writeback_control *wbc)
 357 {
 358         struct inode *inode = page->mapping->host;
 359         unsigned block_start, block_end, blocksize;
 360         struct ext4_io_page *io_page;
 361         struct buffer_head *bh, *head;
 362         int ret = 0;
 363
 364         blocksize = 1 << inode->i_blkbits;
 365
 366         BUG_ON(!PageLocked(page));
 367         BUG_ON(PageWriteback(page));
 368
 369         io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS);
 370         if (!io_page) {
 371                 set_page_dirty(page);
 372                 unlock_page(page);
 373                 return -ENOMEM;
 374         }
 375         io_page->p_page = page;
 376         atomic_set(&io_page->p_count, 1);
 377         get_page(page);
 378         set_page_writeback(page);
 379         ClearPageError(page);
 380
 381         for (bh = head = page_buffers(page), block_start = 0;
 382              bh != head || !block_start;
 383              block_start = block_end, bh = bh->b_this_page) {
 384
 385                 block_end = block_start + blocksize;
 386                 if (block_start >= len) {
 387                         /*
 388                          * Comments copied from block_write_full_page_endio:
 389                          *
 390                          * The page straddles i_size.  It must be zeroed out on
 391                          * each and every writepage invocation because it may
 392                          * be mmapped.  "A file is mapped in multiples of the
 393                          * page size.  For a file that is not a multiple of
 394                          * the  page size, the remaining memory is zeroed when
 395                          * mapped, and writes to that region are not written
 396                          * out to the file."
 397                          */
 398                         zero_user_segment(page, block_start, block_end);
 399                         clear_buffer_dirty(bh);
 400                         set_buffer_uptodate(bh);
 401                         continue;
 402                 }
 403                 clear_buffer_dirty(bh);
 404                 ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
 405                 if (ret) {
 406                         /*
 407                          * We only get here on ENOMEM.  Not much else
 408                          * we can do but mark the page as dirty, and
 409                          * better luck next time.
 410                          */
 411                         set_page_dirty(page);
 412                         break;
 413                 }
 414         }
 415         unlock_page(page);
 416         /*
 417          * If the page was truncated before we could do the writeback,
 418          * or we had a memory allocation error while trying to write
 419          * the first buffer head, we won't have submitted any pages for
 420          * I/O.  In that case we need to make sure we've cleared the
 421          * PageWriteback bit from the page to prevent the system from
 422          * wedging later on.
 423          */
 424         put_io_page(io_page);
 425         return ret;
 426 }