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_size = PAGE_SIZE;
  30         bio.bi_bdev = bdev;
  31         bio.bi_sector = page->index * (PAGE_SIZE >> 9);
  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 = bio->bi_io_vec + bio->bi_vcnt - 1;
  60         struct super_block *sb = bio->bi_private;
  61         struct logfs_super *super = logfs_super(sb);
  62         struct page *page;
  63
  64         BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
  65         BUG_ON(err);
  66         BUG_ON(bio->bi_vcnt == 0);
  67         do {
  68                 page = bvec->bv_page;
  69                 if (--bvec >= bio->bi_io_vec)
  70                         prefetchw(&bvec->bv_page->flags);
  71
  72                 end_page_writeback(page);
  73                 page_cache_release(page);
  74         } while (bvec >= bio->bi_io_vec);
  75         bio_put(bio);
  76         if (atomic_dec_and_test(&super->s_pending_writes))
  77                 wake_up(&wq);
  78 }
  79
  80 static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
  81                 size_t nr_pages)
  82 {
  83         struct logfs_super *super = logfs_super(sb);
  84         struct address_space *mapping = super->s_mapping_inode->i_mapping;
  85         struct bio *bio;
  86         struct page *page;
  87         unsigned int max_pages;
  88         int i;
  89
  90         max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
  91
  92         bio = bio_alloc(GFP_NOFS, max_pages);
  93         BUG_ON(!bio);
  94
  95         for (i = 0; i < nr_pages; i++) {
  96                 if (i >= max_pages) {
  97                         /* Block layer cannot split bios :( */
  98                         bio->bi_vcnt = i;
  99                         bio->bi_size = i * PAGE_SIZE;
 100                         bio->bi_bdev = super->s_bdev;
 101                         bio->bi_sector = ofs >> 9;
 102                         bio->bi_private = sb;
 103                         bio->bi_end_io = writeseg_end_io;
 104                         atomic_inc(&super->s_pending_writes);
 105                         submit_bio(WRITE, bio);
 106
 107                         ofs += i * PAGE_SIZE;
 108                         index += i;
 109                         nr_pages -= i;
 110                         i = 0;
 111
 112                         bio = bio_alloc(GFP_NOFS, max_pages);
 113                         BUG_ON(!bio);
 114                 }
 115                 page = find_lock_page(mapping, index + i);
 116                 BUG_ON(!page);
 117                 bio->bi_io_vec[i].bv_page = page;
 118                 bio->bi_io_vec[i].bv_len = PAGE_SIZE;
 119                 bio->bi_io_vec[i].bv_offset = 0;
 120
 121                 BUG_ON(PageWriteback(page));
 122                 set_page_writeback(page);
 123                 unlock_page(page);
 124         }
 125         bio->bi_vcnt = nr_pages;
 126         bio->bi_size = nr_pages * PAGE_SIZE;
 127         bio->bi_bdev = super->s_bdev;
 128         bio->bi_sector = ofs >> 9;
 129         bio->bi_private = sb;
 130         bio->bi_end_io = writeseg_end_io;
 131         atomic_inc(&super->s_pending_writes);
 132         submit_bio(WRITE, bio);
 133         return 0;
 134 }
 135
 136 static void bdev_writeseg(struct super_block *sb, u64 ofs, size_t len)
 137 {
 138         struct logfs_super *super = logfs_super(sb);
 139         int head;
 140
 141         BUG_ON(super->s_flags & LOGFS_SB_FLAG_RO);
 142
 143         if (len == 0) {
 144                 /* This can happen when the object fit perfectly into a
 145                  * segment, the segment gets written per sync and subsequently
 146                  * closed.
 147                  */
 148                 return;
 149         }
 150         head = ofs & (PAGE_SIZE - 1);
 151         if (head) {
 152                 ofs -= head;
 153                 len += head;
 154         }
 155         len = PAGE_ALIGN(len);
 156         __bdev_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
 157 }
 158
 159
 160 static void erase_end_io(struct bio *bio, int err)
 161 {
 162         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 163         struct super_block *sb = bio->bi_private;
 164         struct logfs_super *super = logfs_super(sb);
 165
 166         BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
 167         BUG_ON(err);
 168         BUG_ON(bio->bi_vcnt == 0);
 169         bio_put(bio);
 170         if (atomic_dec_and_test(&super->s_pending_writes))
 171                 wake_up(&wq);
 172 }
 173
 174 static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
 175                 size_t nr_pages)
 176 {
 177         struct logfs_super *super = logfs_super(sb);
 178         struct bio *bio;
 179         unsigned int max_pages;
 180         int i;
 181
 182         max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
 183
 184         bio = bio_alloc(GFP_NOFS, max_pages);
 185         BUG_ON(!bio);
 186
 187         for (i = 0; i < nr_pages; i++) {
 188                 if (i >= max_pages) {
 189                         /* Block layer cannot split bios :( */
 190                         bio->bi_vcnt = i;
 191                         bio->bi_size = i * PAGE_SIZE;
 192                         bio->bi_bdev = super->s_bdev;
 193                         bio->bi_sector = ofs >> 9;
 194                         bio->bi_private = sb;
 195                         bio->bi_end_io = erase_end_io;
 196                         atomic_inc(&super->s_pending_writes);
 197                         submit_bio(WRITE, bio);
 198
 199                         ofs += i * PAGE_SIZE;
 200                         index += i;
 201                         nr_pages -= i;
 202                         i = 0;
 203
 204                         bio = bio_alloc(GFP_NOFS, max_pages);
 205                         BUG_ON(!bio);
 206                 }
 207                 bio->bi_io_vec[i].bv_page = super->s_erase_page;
 208                 bio->bi_io_vec[i].bv_len = PAGE_SIZE;
 209                 bio->bi_io_vec[i].bv_offset = 0;
 210         }
 211         bio->bi_vcnt = nr_pages;
 212         bio->bi_size = nr_pages * PAGE_SIZE;
 213         bio->bi_bdev = super->s_bdev;
 214         bio->bi_sector = ofs >> 9;
 215         bio->bi_private = sb;
 216         bio->bi_end_io = erase_end_io;
 217         atomic_inc(&super->s_pending_writes);
 218         submit_bio(WRITE, bio);
 219         return 0;
 220 }
 221
 222 static int bdev_erase(struct super_block *sb, loff_t to, size_t len,
 223                 int ensure_write)
 224 {
 225         struct logfs_super *super = logfs_super(sb);
 226
 227         BUG_ON(to & (PAGE_SIZE - 1));
 228         BUG_ON(len & (PAGE_SIZE - 1));
 229
 230         if (super->s_flags & LOGFS_SB_FLAG_RO)
 231                 return -EROFS;
 232
 233         if (ensure_write) {
 234                 /*
 235                  * Object store doesn't care whether erases happen or not.
 236                  * But for the journal they are required.  Otherwise a scan
 237                  * can find an old commit entry and assume it is the current
 238                  * one, travelling back in time.
 239                  */
 240                 do_erase(sb, to, to >> PAGE_SHIFT, len >> PAGE_SHIFT);
 241         }
 242
 243         return 0;
 244 }
 245
 246 static void bdev_sync(struct super_block *sb)
 247 {
 248         struct logfs_super *super = logfs_super(sb);
 249
 250         wait_event(wq, atomic_read(&super->s_pending_writes) == 0);
 251 }
 252
 253 static struct page *bdev_find_first_sb(struct super_block *sb, u64 *ofs)
 254 {
 255         struct logfs_super *super = logfs_super(sb);
 256         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 257         filler_t *filler = bdev_readpage;
 258
 259         *ofs = 0;
 260         return read_cache_page(mapping, 0, filler, sb);
 261 }
 262
 263 static struct page *bdev_find_last_sb(struct super_block *sb, u64 *ofs)
 264 {
 265         struct logfs_super *super = logfs_super(sb);
 266         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 267         filler_t *filler = bdev_readpage;
 268         u64 pos = (super->s_bdev->bd_inode->i_size & ~0xfffULL) - 0x1000;
 269         pgoff_t index = pos >> PAGE_SHIFT;
 270
 271         *ofs = pos;
 272         return read_cache_page(mapping, index, filler, sb);
 273 }
 274
 275 static int bdev_write_sb(struct super_block *sb, struct page *page)
 276 {
 277         struct block_device *bdev = logfs_super(sb)->s_bdev;
 278
 279         /* Nothing special to do for block devices. */
 280         return sync_request(page, bdev, WRITE);
 281 }
 282
 283 static void bdev_put_device(struct logfs_super *s)
 284 {
 285         blkdev_put(s->s_bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 286 }
 287
 288 static int bdev_can_write_buf(struct super_block *sb, u64 ofs)
 289 {
 290         return 0;
 291 }
 292
 293 static const struct logfs_device_ops bd_devops = {
 294         .find_first_sb  = bdev_find_first_sb,
 295         .find_last_sb   = bdev_find_last_sb,
 296         .write_sb       = bdev_write_sb,
 297         .readpage       = bdev_readpage,
 298         .writeseg       = bdev_writeseg,
 299         .erase          = bdev_erase,
 300         .can_write_buf  = bdev_can_write_buf,
 301         .sync           = bdev_sync,
 302         .put_device     = bdev_put_device,
 303 };
 304
 305 int logfs_get_sb_bdev(struct logfs_super *p, struct file_system_type *type,
 306                 const char *devname)
 307 {
 308         struct block_device *bdev;
 309
 310         bdev = blkdev_get_by_path(devname, FMODE_READ|FMODE_WRITE|FMODE_EXCL,
 311                                   type);
 312         if (IS_ERR(bdev))
 313                 return PTR_ERR(bdev);
 314
 315         if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
 316                 int mtdnr = MINOR(bdev->bd_dev);
 317                 blkdev_put(bdev, FMODE_READ|FMODE_WRITE|FMODE_EXCL);
 318                 return logfs_get_sb_mtd(p, mtdnr);
 319         }
 320
 321         p->s_bdev = bdev;
 322         p->s_mtd = NULL;
 323         p->s_devops = &bd_devops;
 324         return 0;
 325 }