kernel/fs/logfs/dev_bdev.c

   1 /*
   2  * fs/logfs/dev_bdev.c  - Device access methods for block devices
   3  *
   4  * As should be obvious for Linux kernel code, license is GPLv2
   5  *
   6  * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
   7  */
   8 #include "logfs.h"
   9 #include <linux/bio.h>
  10 #include <linux/blkdev.h>
  11 #include <linux/buffer_head.h>
  12 #include <linux/gfp.h>
  13 #include <linux/prefetch.h>
  14
  15 #define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
  16
  17 static int sync_request(struct page *page, struct block_device *bdev, int rw)
  18 {
  19         struct bio bio;
  20         struct bio_vec bio_vec;
  21
  22         bio_init(&bio);
  23         bio.bi_max_vecs = 1;
  24         bio.bi_io_vec = &bio_vec;
  25         bio_vec.bv_page = page;
  26         bio_vec.bv_len = PAGE_SIZE;
  27         bio_vec.bv_offset = 0;
  28         bio.bi_vcnt = 1;
  29         bio.bi_bdev = bdev;
  30         bio.bi_iter.bi_sector = page->index * (PAGE_SIZE >> 9);
  31         bio.bi_iter.bi_size = PAGE_SIZE;
  32
  33         return submit_bio_wait(rw, &bio);
  34 }
  35
  36 static int bdev_readpage(void *_sb, struct page *page)
  37 {
  38         struct super_block *sb = _sb;
  39         struct block_device *bdev = logfs_super(sb)->s_bdev;
  40         int err;
  41
  42         err = sync_request(page, bdev, READ);
  43         if (err) {
  44                 ClearPageUptodate(page);
  45                 SetPageError(page);
  46         } else {
  47                 SetPageUptodate(page);
  48                 ClearPageError(page);
  49         }
  50         unlock_page(page);
  51         return err;
  52 }
  53
  54 static DECLARE_WAIT_QUEUE_HEAD(wq);
  55
  56 static void writeseg_end_io(struct bio *bio, int err)
  57 {
  58         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  59         struct bio_vec *bvec;
  60         int i;
  61         struct super_block *sb = bio->bi_private;
  62         struct logfs_super *super = logfs_super(sb);
  63
  64         BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
  65         BUG_ON(err);
  66
  67         bio_for_each_segment_all(bvec, bio, i) {
  68                 end_page_writeback(bvec->bv_page);
  69                 page_cache_release(bvec->bv_page);
  70         }
  71         bio_put(bio);
  72         if (atomic_dec_and_test(&super->s_pending_writes))
  73                 wake_up(&wq);
  74 }
  75
  76 static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
  77                 size_t nr_pages)
  78 {
  79         struct logfs_super *super = logfs_super(sb);
  80         struct address_space *mapping = super->s_mapping_inode->i_mapping;
  81         struct bio *bio;
  82         struct page *page;
  83         unsigned int max_pages;
  84         int i;
  85
  86         max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
  87
  88         bio = bio_alloc(GFP_NOFS, max_pages);
  89         BUG_ON(!bio);
  90
  91         for (i = 0; i < nr_pages; i++) {
  92                 if (i >= max_pages) {
  93                         /* Block layer cannot split bios :( */
  94                         bio->bi_vcnt = i;
  95                         bio->bi_iter.bi_size = i * PAGE_SIZE;
  96                         bio->bi_bdev = super->s_bdev;
  97                         bio->bi_iter.bi_sector = ofs >> 9;
  98                         bio->bi_private = sb;
  99                         bio->bi_end_io = writeseg_end_io;
 100                         atomic_inc(&super->s_pending_writes);
 101                         submit_bio(WRITE, bio);
 102
 103                         ofs += i * PAGE_SIZE;
 104                         index += i;
 105                         nr_pages -= i;
 106                         i = 0;
 107
 108                         bio = bio_alloc(GFP_NOFS, max_pages);
 109                         BUG_ON(!bio);
 110                 }
 111                 page = find_lock_page(mapping, index + i);
 112                 BUG_ON(!page);
 113                 bio->bi_io_vec[i].bv_page = page;
 114                 bio->bi_io_vec[i].bv_len = PAGE_SIZE;
 115                 bio->bi_io_vec[i].bv_offset = 0;
 116
 117                 BUG_ON(PageWriteback(page));
 118                 set_page_writeback(page);
 119                 unlock_page(page);
 120         }
 121         bio->bi_vcnt = nr_pages;
 122         bio->bi_iter.bi_size = nr_pages * PAGE_SIZE;
 123         bio->bi_bdev = super->s_bdev;
 124         bio->bi_iter.bi_sector = ofs >> 9;
 125         bio->bi_private = sb;
 126         bio->bi_end_io = writeseg_end_io;
 127         atomic_inc(&super->s_pending_writes);
 128         submit_bio(WRITE, bio);
 129         return 0;
 130 }
 131
 132 static void bdev_writeseg(struct super_block *sb, u64 ofs, size_t len)
 133 {
 134         struct logfs_super *super = logfs_super(sb);
 135         int head;
 136
 137         BUG_ON(super->s_flags & LOGFS_SB_FLAG_RO);
 138
 139         if (len == 0) {
 140                 /* This can happen when the object fit perfectly into a
 141                  * segment, the segment gets written per sync and subsequently
 142                  * closed.
 143                  */
 144                 return;
 145         }
 146         head = ofs & (PAGE_SIZE - 1);
 147         if (head) {
 148                 ofs -= head;
 149                 len += head;
 150         }
 151         len = PAGE_ALIGN(len);
 152         __bdev_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
 153 }
 154
 155
 156 static void erase_end_io(struct bio *bio, int err)
 157 {
 158         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 159         struct super_block *sb = bio->bi_private;
 160         struct logfs_super *super = logfs_super(sb);
 161
 162         BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
 163         BUG_ON(err);
 164         BUG_ON(bio->bi_vcnt == 0);
 165         bio_put(bio);
 166         if (atomic_dec_and_test(&super->s_pending_writes))
 167                 wake_up(&wq);
 168 }
 169
 170 static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
 171                 size_t nr_pages)
 172 {
 173         struct logfs_super *super = logfs_super(sb);
 174         struct bio *bio;
 175         unsigned int max_pages;
 176         int i;
 177
 178         max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
 179
 180         bio = bio_alloc(GFP_NOFS, max_pages);
 181         BUG_ON(!bio);
 182
 183         for (i = 0; i < nr_pages; i++) {
 184                 if (i >= max_pages) {
 185                         /* Block layer cannot split bios :( */
 186                         bio->bi_vcnt = i;
 187                         bio->bi_iter.bi_size = i * PAGE_SIZE;
 188                         bio->bi_bdev = super->s_bdev;
 189                         bio->bi_iter.bi_sector = ofs >> 9;
 190                         bio->bi_private = sb;
 191                         bio->bi_end_io = erase_end_io;
 192                         atomic_inc(&super->s_pending_writes);
 193                         submit_bio(WRITE, bio);
 194
 195                         ofs += i * PAGE_SIZE;
 196                         index += i;
 197                         nr_pages -= i;
 198                         i = 0;
 199
 200                         bio = bio_alloc(GFP_NOFS, max_pages);
 201                         BUG_ON(!bio);
 202                 }
 203                 bio->bi_io_vec[i].bv_page = super->s_erase_page;
 204                 bio->bi_io_vec[i].bv_len = PAGE_SIZE;
 205                 bio->bi_io_vec[i].bv_offset = 0;
 206         }
 207         bio->bi_vcnt = nr_pages;
 208         bio->bi_iter.bi_size = nr_pages * PAGE_SIZE;
 209         bio->bi_bdev = super->s_bdev;
 210         bio->bi_iter.bi_sector = ofs >> 9;
 211         bio->bi_private = sb;
 212         bio->bi_end_io = erase_end_io;
 213         atomic_inc(&super->s_pending_writes);
 214         submit_bio(WRITE, bio);
 215         return 0;
 216 }
 217
 218 static int bdev_erase(struct super_block *sb, loff_t to, size_t len,
 219                 int ensure_write)
 220 {
 221         struct logfs_super *super = logfs_super(sb);
 222
 223         BUG_ON(to & (PAGE_SIZE - 1));
 224         BUG_ON(len & (PAGE_SIZE - 1));
 225
 226         if (super->s_flags & LOGFS_SB_FLAG_RO)
 227                 return -EROFS;
 228
 229         if (ensure_write) {
 230                 /*
 231                  * Object store doesn't care whether erases happen or not.
 232                  * But for the journal they are required.  Otherwise a scan
 233                  * can find an old commit entry and assume it is the current
 234                  * one, travelling back in time.
 235                  */
 236                 do_erase(sb, to, to >> PAGE_SHIFT, len >> PAGE_SHIFT);
 237         }
 238
 239         return 0;
 240 }
 241
 242 static void bdev_sync(struct super_block *sb)
 243 {
 244         struct logfs_super *super = logfs_super(sb);
 245
 246         wait_event(wq, atomic_read(&super->s_pending_writes) == 0);
 247 }
 248
 249 static struct page *bdev_find_first_sb(struct super_block *sb, u64 *ofs)
 250 {
 251         struct logfs_super *super = logfs_super(sb);
 252         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 253         filler_t *filler = bdev_readpage;
 254
 255         *ofs = 0;
 256         return read_cache_page(mapping, 0, filler, sb);
 257 }
 258
 259 static struct page *bdev_find_last_sb(struct super_block *sb, u64 *ofs)
 260 {
 261         struct logfs_super *super = logfs_super(sb);
 262         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 263         filler_t *filler = bdev_readpage;
 264         u64 pos = (super->s_bdev->bd_inode->i_size & ~0xfffULL) - 0x1000;
 265         pgoff_t index = pos >> PAGE_SHIFT;
 266
 267         *ofs = pos;
 268         return read_cache_page(mapping, index, filler, sb);
 269 }
 270
 271 static int bdev_write_sb(struct super_block *sb, struct page *page)
 272 {
 273         struct block_device *bdev = logfs_super(sb)->s_bdev;
 274
 275         /* Nothing special to do for block devices. */
 276         return sync_request(page, bdev, WRITE);
 277 }
 278
 279 static void bdev_put_device(struct logfs_super *s)
 280 {
 281         blkdev_put(s->s_bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 282 }
 283
 284 static int bdev_can_write_buf(struct super_block *sb, u64 ofs)
 285 {
 286         return 0;
 287 }
 288
 289 static const struct logfs_device_ops bd_devops = {
 290         .find_first_sb  = bdev_find_first_sb,
 291         .find_last_sb   = bdev_find_last_sb,
 292         .write_sb       = bdev_write_sb,
 293         .readpage       = bdev_readpage,
 294         .writeseg       = bdev_writeseg,
 295         .erase          = bdev_erase,
 296         .can_write_buf  = bdev_can_write_buf,
 297         .sync           = bdev_sync,
 298         .put_device     = bdev_put_device,
 299 };
 300
 301 int logfs_get_sb_bdev(struct logfs_super *p, struct file_system_type *type,
 302                 const char *devname)
 303 {
 304         struct block_device *bdev;
 305
 306         bdev = blkdev_get_by_path(devname, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
 307                                   type);
 308         if (IS_ERR(bdev))
 309                 return PTR_ERR(bdev);
 310
 311         if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
 312                 int mtdnr = MINOR(bdev->bd_dev);
 313                 blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 314                 return logfs_get_sb_mtd(p, mtdnr);
 315         }
 316
 317         p->s_bdev = bdev;
 318         p->s_mtd = NULL;
 319         p->s_devops = &bd_devops;
 320         return 0;
 321 }