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
  14 #define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
  15
  16 static void request_complete(struct bio *bio, int err)
  17 {
  18         complete((struct completion *)bio->bi_private);
  19 }
  20
  21 static int sync_request(struct page *page, struct block_device *bdev, int rw)
  22 {
  23         struct bio bio;
  24         struct bio_vec bio_vec;
  25         struct completion complete;
  26
  27         bio_init(&bio);
  28         bio.bi_io_vec = &bio_vec;
  29         bio_vec.bv_page = page;
  30         bio_vec.bv_len = PAGE_SIZE;
  31         bio_vec.bv_offset = 0;
  32         bio.bi_vcnt = 1;
  33         bio.bi_idx = 0;
  34         bio.bi_size = PAGE_SIZE;
  35         bio.bi_bdev = bdev;
  36         bio.bi_sector = page->index * (PAGE_SIZE >> 9);
  37         init_completion(&complete);
  38         bio.bi_private = &complete;
  39         bio.bi_end_io = request_complete;
  40
  41         submit_bio(rw, &bio);
  42         generic_unplug_device(bdev_get_queue(bdev));
  43         wait_for_completion(&complete);
  44         return test_bit(BIO_UPTODATE, &bio.bi_flags) ? 0 : -EIO;
  45 }
  46
  47 static int bdev_readpage(void *_sb, struct page *page)
  48 {
  49         struct super_block *sb = _sb;
  50         struct block_device *bdev = logfs_super(sb)->s_bdev;
  51         int err;
  52
  53         err = sync_request(page, bdev, READ);
  54         if (err) {
  55                 ClearPageUptodate(page);
  56                 SetPageError(page);
  57         } else {
  58                 SetPageUptodate(page);
  59                 ClearPageError(page);
  60         }
  61         unlock_page(page);
  62         return err;
  63 }
  64
  65 static DECLARE_WAIT_QUEUE_HEAD(wq);
  66
  67 static void writeseg_end_io(struct bio *bio, int err)
  68 {
  69         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
  70         struct bio_vec *bvec = bio->bi_io_vec + bio->bi_vcnt - 1;
  71         struct super_block *sb = bio->bi_private;
  72         struct logfs_super *super = logfs_super(sb);
  73         struct page *page;
  74
  75         BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
  76         BUG_ON(err);
  77         BUG_ON(bio->bi_vcnt == 0);
  78         do {
  79                 page = bvec->bv_page;
  80                 if (--bvec >= bio->bi_io_vec)
  81                         prefetchw(&bvec->bv_page->flags);
  82
  83                 end_page_writeback(page);
  84         } while (bvec >= bio->bi_io_vec);
  85         bio_put(bio);
  86         if (atomic_dec_and_test(&super->s_pending_writes))
  87                 wake_up(&wq);
  88 }
  89
  90 static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
  91                 size_t nr_pages)
  92 {
  93         struct logfs_super *super = logfs_super(sb);
  94         struct address_space *mapping = super->s_mapping_inode->i_mapping;
  95         struct bio *bio;
  96         struct page *page;
  97         struct request_queue *q = bdev_get_queue(sb->s_bdev);
  98         unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
  99         int i;
 100
 101         bio = bio_alloc(GFP_NOFS, max_pages);
 102         BUG_ON(!bio); /* FIXME: handle this */
 103
 104         for (i = 0; i < nr_pages; i++) {
 105                 if (i >= max_pages) {
 106                         /* Block layer cannot split bios :( */
 107                         bio->bi_vcnt = i;
 108                         bio->bi_idx = 0;
 109                         bio->bi_size = i * PAGE_SIZE;
 110                         bio->bi_bdev = super->s_bdev;
 111                         bio->bi_sector = ofs >> 9;
 112                         bio->bi_private = sb;
 113                         bio->bi_end_io = writeseg_end_io;
 114                         atomic_inc(&super->s_pending_writes);
 115                         submit_bio(WRITE, bio);
 116
 117                         ofs += i * PAGE_SIZE;
 118                         index += i;
 119                         nr_pages -= i;
 120                         i = 0;
 121
 122                         bio = bio_alloc(GFP_NOFS, max_pages);
 123                         BUG_ON(!bio);
 124                 }
 125                 page = find_lock_page(mapping, index + i);
 126                 BUG_ON(!page);
 127                 bio->bi_io_vec[i].bv_page = page;
 128                 bio->bi_io_vec[i].bv_len = PAGE_SIZE;
 129                 bio->bi_io_vec[i].bv_offset = 0;
 130
 131                 BUG_ON(PageWriteback(page));
 132                 set_page_writeback(page);
 133                 unlock_page(page);
 134         }
 135         bio->bi_vcnt = nr_pages;
 136         bio->bi_idx = 0;
 137         bio->bi_size = nr_pages * PAGE_SIZE;
 138         bio->bi_bdev = super->s_bdev;
 139         bio->bi_sector = ofs >> 9;
 140         bio->bi_private = sb;
 141         bio->bi_end_io = writeseg_end_io;
 142         atomic_inc(&super->s_pending_writes);
 143         submit_bio(WRITE, bio);
 144         return 0;
 145 }
 146
 147 static void bdev_writeseg(struct super_block *sb, u64 ofs, size_t len)
 148 {
 149         struct logfs_super *super = logfs_super(sb);
 150         int head;
 151
 152         BUG_ON(super->s_flags & LOGFS_SB_FLAG_RO);
 153
 154         if (len == 0) {
 155                 /* This can happen when the object fit perfectly into a
 156                  * segment, the segment gets written per sync and subsequently
 157                  * closed.
 158                  */
 159                 return;
 160         }
 161         head = ofs & (PAGE_SIZE - 1);
 162         if (head) {
 163                 ofs -= head;
 164                 len += head;
 165         }
 166         len = PAGE_ALIGN(len);
 167         __bdev_writeseg(sb, ofs, ofs >> PAGE_SHIFT, len >> PAGE_SHIFT);
 168         generic_unplug_device(bdev_get_queue(logfs_super(sb)->s_bdev));
 169 }
 170
 171
 172 static void erase_end_io(struct bio *bio, int err)
 173 {
 174         const int uptodate = test_bit(BIO_UPTODATE, &bio->bi_flags);
 175         struct super_block *sb = bio->bi_private;
 176         struct logfs_super *super = logfs_super(sb);
 177
 178         BUG_ON(!uptodate); /* FIXME: Retry io or write elsewhere */
 179         BUG_ON(err);
 180         BUG_ON(bio->bi_vcnt == 0);
 181         bio_put(bio);
 182         if (atomic_dec_and_test(&super->s_pending_writes))
 183                 wake_up(&wq);
 184 }
 185
 186 static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
 187                 size_t nr_pages)
 188 {
 189         struct logfs_super *super = logfs_super(sb);
 190         struct bio *bio;
 191         struct request_queue *q = bdev_get_queue(sb->s_bdev);
 192         unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
 193         int i;
 194
 195         bio = bio_alloc(GFP_NOFS, max_pages);
 196         BUG_ON(!bio); /* FIXME: handle this */
 197
 198         for (i = 0; i < nr_pages; i++) {
 199                 if (i >= max_pages) {
 200                         /* Block layer cannot split bios :( */
 201                         bio->bi_vcnt = i;
 202                         bio->bi_idx = 0;
 203                         bio->bi_size = i * PAGE_SIZE;
 204                         bio->bi_bdev = super->s_bdev;
 205                         bio->bi_sector = ofs >> 9;
 206                         bio->bi_private = sb;
 207                         bio->bi_end_io = erase_end_io;
 208                         atomic_inc(&super->s_pending_writes);
 209                         submit_bio(WRITE, bio);
 210
 211                         ofs += i * PAGE_SIZE;
 212                         index += i;
 213                         nr_pages -= i;
 214                         i = 0;
 215
 216                         bio = bio_alloc(GFP_NOFS, max_pages);
 217                         BUG_ON(!bio);
 218                 }
 219                 bio->bi_io_vec[i].bv_page = super->s_erase_page;
 220                 bio->bi_io_vec[i].bv_len = PAGE_SIZE;
 221                 bio->bi_io_vec[i].bv_offset = 0;
 222         }
 223         bio->bi_vcnt = nr_pages;
 224         bio->bi_idx = 0;
 225         bio->bi_size = nr_pages * PAGE_SIZE;
 226         bio->bi_bdev = super->s_bdev;
 227         bio->bi_sector = ofs >> 9;
 228         bio->bi_private = sb;
 229         bio->bi_end_io = erase_end_io;
 230         atomic_inc(&super->s_pending_writes);
 231         submit_bio(WRITE, bio);
 232         return 0;
 233 }
 234
 235 static int bdev_erase(struct super_block *sb, loff_t to, size_t len,
 236                 int ensure_write)
 237 {
 238         struct logfs_super *super = logfs_super(sb);
 239
 240         BUG_ON(to & (PAGE_SIZE - 1));
 241         BUG_ON(len & (PAGE_SIZE - 1));
 242
 243         if (super->s_flags & LOGFS_SB_FLAG_RO)
 244                 return -EROFS;
 245
 246         if (ensure_write) {
 247                 /*
 248                  * Object store doesn't care whether erases happen or not.
 249                  * But for the journal they are required.  Otherwise a scan
 250                  * can find an old commit entry and assume it is the current
 251                  * one, travelling back in time.
 252                  */
 253                 do_erase(sb, to, to >> PAGE_SHIFT, len >> PAGE_SHIFT);
 254         }
 255
 256         return 0;
 257 }
 258
 259 static void bdev_sync(struct super_block *sb)
 260 {
 261         struct logfs_super *super = logfs_super(sb);
 262
 263         wait_event(wq, atomic_read(&super->s_pending_writes) == 0);
 264 }
 265
 266 static struct page *bdev_find_first_sb(struct super_block *sb, u64 *ofs)
 267 {
 268         struct logfs_super *super = logfs_super(sb);
 269         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 270         filler_t *filler = bdev_readpage;
 271
 272         *ofs = 0;
 273         return read_cache_page(mapping, 0, filler, sb);
 274 }
 275
 276 static struct page *bdev_find_last_sb(struct super_block *sb, u64 *ofs)
 277 {
 278         struct logfs_super *super = logfs_super(sb);
 279         struct address_space *mapping = super->s_mapping_inode->i_mapping;
 280         filler_t *filler = bdev_readpage;
 281         u64 pos = (super->s_bdev->bd_inode->i_size & ~0xfffULL) - 0x1000;
 282         pgoff_t index = pos >> PAGE_SHIFT;
 283
 284         *ofs = pos;
 285         return read_cache_page(mapping, index, filler, sb);
 286 }
 287
 288 static int bdev_write_sb(struct super_block *sb, struct page *page)
 289 {
 290         struct block_device *bdev = logfs_super(sb)->s_bdev;
 291
 292         /* Nothing special to do for block devices. */
 293         return sync_request(page, bdev, WRITE);
 294 }
 295
 296 static void bdev_put_device(struct super_block *sb)
 297 {
 298         close_bdev_exclusive(logfs_super(sb)->s_bdev, FMODE_READ|FMODE_WRITE);
 299 }
 300
 301 static const struct logfs_device_ops bd_devops = {
 302         .find_first_sb  = bdev_find_first_sb,
 303         .find_last_sb   = bdev_find_last_sb,
 304         .write_sb       = bdev_write_sb,
 305         .readpage       = bdev_readpage,
 306         .writeseg       = bdev_writeseg,
 307         .erase          = bdev_erase,
 308         .sync           = bdev_sync,
 309         .put_device     = bdev_put_device,
 310 };
 311
 312 int logfs_get_sb_bdev(struct file_system_type *type, int flags,
 313                 const char *devname, struct vfsmount *mnt)
 314 {
 315         struct block_device *bdev;
 316
 317         bdev = open_bdev_exclusive(devname, FMODE_READ|FMODE_WRITE, type);
 318         if (IS_ERR(bdev))
 319                 return PTR_ERR(bdev);
 320
 321         if (MAJOR(bdev->bd_dev) == MTD_BLOCK_MAJOR) {
 322                 int mtdnr = MINOR(bdev->bd_dev);
 323                 close_bdev_exclusive(bdev, FMODE_READ|FMODE_WRITE);
 324                 return logfs_get_sb_mtd(type, flags, mtdnr, mnt);
 325         }
 326
 327         return logfs_get_sb_device(type, flags, NULL, bdev, &bd_devops, mnt);
 328 }