linux/mm/page_io.c
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   1/*
   2 *  linux/mm/page_io.c
   3 *
   4 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   5 *
   6 *  Swap reorganised 29.12.95, 
   7 *  Asynchronous swapping added 30.12.95. Stephen Tweedie
   8 *  Removed race in async swapping. 14.4.1996. Bruno Haible
   9 *  Add swap of shared pages through the page cache. 20.2.1998. Stephen Tweedie
  10 *  Always use brw_page, life becomes simpler. 12 May 1998 Eric Biederman
  11 */
  12
  13#include <linux/mm.h>
  14#include <linux/kernel_stat.h>
  15#include <linux/gfp.h>
  16#include <linux/pagemap.h>
  17#include <linux/swap.h>
  18#include <linux/bio.h>
  19#include <linux/swapops.h>
  20#include <linux/buffer_head.h>
  21#include <linux/writeback.h>
  22#include <linux/frontswap.h>
  23#include <asm/pgtable.h>
  24
  25static struct bio *get_swap_bio(gfp_t gfp_flags,
  26                                struct page *page, bio_end_io_t end_io)
  27{
  28        struct bio *bio;
  29
  30        bio = bio_alloc(gfp_flags, 1);
  31        if (bio) {
  32                bio->bi_sector = map_swap_page(page, &bio->bi_bdev);
  33                bio->bi_sector <<= PAGE_SHIFT - 9;
  34                bio->bi_io_vec[0].bv_page = page;
  35                bio->bi_io_vec[0].bv_len = PAGE_SIZE;
  36                bio->bi_io_vec[0].bv_offset = 0;
  37                bio->bi_vcnt = 1;
  38                bio->bi_idx = 0;
  39                bio->bi_size = PAGE_SIZE;
  40                bio->bi_end_io = end_io;
  41        }
  42        return bio;
  43}
  44
  45static void end_swap_bio_write(struct bio *bio, int err)
  46{
  47        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  48        struct page *page = bio->bi_io_vec[0].bv_page;
  49
  50        if (!uptodate) {
  51                SetPageError(page);
  52                /*
  53                 * We failed to write the page out to swap-space.
  54                 * Re-dirty the page in order to avoid it being reclaimed.
  55                 * Also print a dire warning that things will go BAD (tm)
  56                 * very quickly.
  57                 *
  58                 * Also clear PG_reclaim to avoid rotate_reclaimable_page()
  59                 */
  60                set_page_dirty(page);
  61                printk(KERN_ALERT "Write-error on swap-device (%u:%u:%Lu)\n",
  62                                imajor(bio->bi_bdev->bd_inode),
  63                                iminor(bio->bi_bdev->bd_inode),
  64                                (unsigned long long)bio->bi_sector);
  65                ClearPageReclaim(page);
  66        }
  67        end_page_writeback(page);
  68        bio_put(bio);
  69}
  70
  71void end_swap_bio_read(struct bio *bio, int err)
  72{
  73        const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  74        struct page *page = bio->bi_io_vec[0].bv_page;
  75
  76        if (!uptodate) {
  77                SetPageError(page);
  78                ClearPageUptodate(page);
  79                printk(KERN_ALERT "Read-error on swap-device (%u:%u:%Lu)\n",
  80                                imajor(bio->bi_bdev->bd_inode),
  81                                iminor(bio->bi_bdev->bd_inode),
  82                                (unsigned long long)bio->bi_sector);
  83        } else {
  84                SetPageUptodate(page);
  85        }
  86        unlock_page(page);
  87        bio_put(bio);
  88}
  89
  90int generic_swapfile_activate(struct swap_info_struct *sis,
  91                                struct file *swap_file,
  92                                sector_t *span)
  93{
  94        struct address_space *mapping = swap_file->f_mapping;
  95        struct inode *inode = mapping->host;
  96        unsigned blocks_per_page;
  97        unsigned long page_no;
  98        unsigned blkbits;
  99        sector_t probe_block;
 100        sector_t last_block;
 101        sector_t lowest_block = -1;
 102        sector_t highest_block = 0;
 103        int nr_extents = 0;
 104        int ret;
 105
 106        blkbits = inode->i_blkbits;
 107        blocks_per_page = PAGE_SIZE >> blkbits;
 108
 109        /*
 110         * Map all the blocks into the extent list.  This code doesn't try
 111         * to be very smart.
 112         */
 113        probe_block = 0;
 114        page_no = 0;
 115        last_block = i_size_read(inode) >> blkbits;
 116        while ((probe_block + blocks_per_page) <= last_block &&
 117                        page_no < sis->max) {
 118                unsigned block_in_page;
 119                sector_t first_block;
 120
 121                first_block = bmap(inode, probe_block);
 122                if (first_block == 0)
 123                        goto bad_bmap;
 124
 125                /*
 126                 * It must be PAGE_SIZE aligned on-disk
 127                 */
 128                if (first_block & (blocks_per_page - 1)) {
 129                        probe_block++;
 130                        goto reprobe;
 131                }
 132
 133                for (block_in_page = 1; block_in_page < blocks_per_page;
 134                                        block_in_page++) {
 135                        sector_t block;
 136
 137                        block = bmap(inode, probe_block + block_in_page);
 138                        if (block == 0)
 139                                goto bad_bmap;
 140                        if (block != first_block + block_in_page) {
 141                                /* Discontiguity */
 142                                probe_block++;
 143                                goto reprobe;
 144                        }
 145                }
 146
 147                first_block >>= (PAGE_SHIFT - blkbits);
 148                if (page_no) {  /* exclude the header page */
 149                        if (first_block < lowest_block)
 150                                lowest_block = first_block;
 151                        if (first_block > highest_block)
 152                                highest_block = first_block;
 153                }
 154
 155                /*
 156                 * We found a PAGE_SIZE-length, PAGE_SIZE-aligned run of blocks
 157                 */
 158                ret = add_swap_extent(sis, page_no, 1, first_block);
 159                if (ret < 0)
 160                        goto out;
 161                nr_extents += ret;
 162                page_no++;
 163                probe_block += blocks_per_page;
 164reprobe:
 165                continue;
 166        }
 167        ret = nr_extents;
 168        *span = 1 + highest_block - lowest_block;
 169        if (page_no == 0)
 170                page_no = 1;    /* force Empty message */
 171        sis->max = page_no;
 172        sis->pages = page_no - 1;
 173        sis->highest_bit = page_no - 1;
 174out:
 175        return ret;
 176bad_bmap:
 177        printk(KERN_ERR "swapon: swapfile has holes\n");
 178        ret = -EINVAL;
 179        goto out;
 180}
 181
 182/*
 183 * We may have stale swap cache pages in memory: notice
 184 * them here and get rid of the unnecessary final write.
 185 */
 186int swap_writepage(struct page *page, struct writeback_control *wbc)
 187{
 188        struct bio *bio;
 189        int ret = 0, rw = WRITE;
 190        struct swap_info_struct *sis = page_swap_info(page);
 191
 192        if (try_to_free_swap(page)) {
 193                unlock_page(page);
 194                goto out;
 195        }
 196        if (frontswap_store(page) == 0) {
 197                set_page_writeback(page);
 198                unlock_page(page);
 199                end_page_writeback(page);
 200                goto out;
 201        }
 202
 203        if (sis->flags & SWP_FILE) {
 204                struct kiocb kiocb;
 205                struct file *swap_file = sis->swap_file;
 206                struct address_space *mapping = swap_file->f_mapping;
 207                struct iovec iov = {
 208                        .iov_base = kmap(page),
 209                        .iov_len  = PAGE_SIZE,
 210                };
 211
 212                init_sync_kiocb(&kiocb, swap_file);
 213                kiocb.ki_pos = page_file_offset(page);
 214                kiocb.ki_left = PAGE_SIZE;
 215                kiocb.ki_nbytes = PAGE_SIZE;
 216
 217                set_page_writeback(page);
 218                unlock_page(page);
 219                ret = mapping->a_ops->direct_IO(KERNEL_WRITE,
 220                                                &kiocb, &iov,
 221                                                kiocb.ki_pos, 1);
 222                kunmap(page);
 223                if (ret == PAGE_SIZE) {
 224                        count_vm_event(PSWPOUT);
 225                        ret = 0;
 226                } else {
 227                        /*
 228                         * In the case of swap-over-nfs, this can be a
 229                         * temporary failure if the system has limited
 230                         * memory for allocating transmit buffers.
 231                         * Mark the page dirty and avoid
 232                         * rotate_reclaimable_page but rate-limit the
 233                         * messages but do not flag PageError like
 234                         * the normal direct-to-bio case as it could
 235                         * be temporary.
 236                         */
 237                        set_page_dirty(page);
 238                        ClearPageReclaim(page);
 239                        pr_err_ratelimited("Write error on dio swapfile (%Lu)\n",
 240                                page_file_offset(page));
 241                }
 242                end_page_writeback(page);
 243                return ret;
 244        }
 245
 246        bio = get_swap_bio(GFP_NOIO, page, end_swap_bio_write);
 247        if (bio == NULL) {
 248                set_page_dirty(page);
 249                unlock_page(page);
 250                ret = -ENOMEM;
 251                goto out;
 252        }
 253        if (wbc->sync_mode == WB_SYNC_ALL)
 254                rw |= REQ_SYNC;
 255        count_vm_event(PSWPOUT);
 256        set_page_writeback(page);
 257        unlock_page(page);
 258        submit_bio(rw, bio);
 259out:
 260        return ret;
 261}
 262
 263int swap_readpage(struct page *page)
 264{
 265        struct bio *bio;
 266        int ret = 0;
 267        struct swap_info_struct *sis = page_swap_info(page);
 268
 269        VM_BUG_ON(!PageLocked(page));
 270        VM_BUG_ON(PageUptodate(page));
 271        if (frontswap_load(page) == 0) {
 272                SetPageUptodate(page);
 273                unlock_page(page);
 274                goto out;
 275        }
 276
 277        if (sis->flags & SWP_FILE) {
 278                struct file *swap_file = sis->swap_file;
 279                struct address_space *mapping = swap_file->f_mapping;
 280
 281                ret = mapping->a_ops->readpage(swap_file, page);
 282                if (!ret)
 283                        count_vm_event(PSWPIN);
 284                return ret;
 285        }
 286
 287        bio = get_swap_bio(GFP_KERNEL, page, end_swap_bio_read);
 288        if (bio == NULL) {
 289                unlock_page(page);
 290                ret = -ENOMEM;
 291                goto out;
 292        }
 293        count_vm_event(PSWPIN);
 294        submit_bio(READ, bio);
 295out:
 296        return ret;
 297}
 298
 299int swap_set_page_dirty(struct page *page)
 300{
 301        struct swap_info_struct *sis = page_swap_info(page);
 302
 303        if (sis->flags & SWP_FILE) {
 304                struct address_space *mapping = sis->swap_file->f_mapping;
 305                return mapping->a_ops->set_page_dirty(page);
 306        } else {
 307                return __set_page_dirty_no_writeback(page);
 308        }
 309}
 310
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