hfsplus: use raw bio access for the volume headers

The hfsplus backup volume header is located two blocks from the end of
the device.  In case of device sizes that are not 4k aligned this means
we can't access it using buffer_heads when using the default 4k block
size.

Switch to using raw bios to read/write all buffer headers.  We were not
relying on any caching behaviour of the buffer heads anyway.  Additionally
always read in the backup volume header during mount to verify that we
can actually read it.

Signed-off-by: Christoph Hellwig <hch@tuxera.com>

3 files changed, 131 insertions, 88 deletions

diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index f07aa640c27d..276ddb0fd0fd 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/fs/hfsplus/hfsplus_fs.h
@@ -107,8 +107,8 @@ struct hfsplus_vh;
 struct hfs_btree;
 
 struct hfsplus_sb_info {
-        struct buffer_head *s_vhbh;
         struct hfsplus_vh *s_vhdr;
+        struct hfsplus_vh *s_backup_vhdr;
         struct hfs_btree *ext_tree;
         struct hfs_btree *cat_tree;
         struct hfs_btree *attr_tree;
@@ -118,7 +118,8 @@ struct hfsplus_sb_info {
 
         /* Runtime variables */
         u32 blockoffset;
-        u32 sect_count;
+        sector_t part_start;
+        sector_t sect_count;
         int fs_shift;
 
         /* immutable data from the volume header */
@@ -385,8 +386,9 @@ int hfsplus_compare_dentry(struct dentry *dentry, struct qstr *s1, struct qstr *
 
 /* wrapper.c */
 int hfsplus_read_wrapper(struct super_block *);
-
 int hfs_part_find(struct super_block *, sector_t *, sector_t *);
+int hfsplus_submit_bio(struct block_device *bdev, sector_t sector,
+                void *data, int rw);
 
 /* access macros */
 static inline struct hfsplus_sb_info *HFSPLUS_SB(struct super_block *sb)
diff --git a/fs/hfsplus/super.c b/fs/hfsplus/super.c
index 6a2349058618..fe8f7bffbea5 100644
--- a/fs/hfsplus/super.c
+++ b/fs/hfsplus/super.c
@@ -157,45 +157,40 @@ int hfsplus_sync_fs(struct super_block *sb, int wait)
 {
         struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
         struct hfsplus_vh *vhdr = sbi->s_vhdr;
+        int write_backup = 0;
+        int error, error2;
 
         dprint(DBG_SUPER, "hfsplus_write_super\n");
 
-        mutex_lock(&sbi->vh_mutex);
-        mutex_lock(&sbi->alloc_mutex);
         sb->s_dirt = 0;
 
+        mutex_lock(&sbi->vh_mutex);
+        mutex_lock(&sbi->alloc_mutex);
         vhdr->free_blocks = cpu_to_be32(sbi->free_blocks);
         vhdr->next_cnid = cpu_to_be32(sbi->next_cnid);
         vhdr->folder_count = cpu_to_be32(sbi->folder_count);
         vhdr->file_count = cpu_to_be32(sbi->file_count);
 
-        mark_buffer_dirty(sbi->s_vhbh);
         if (test_and_clear_bit(HFSPLUS_SB_WRITEBACKUP, &sbi->flags)) {
-                if (sbi->sect_count) {
-                        struct buffer_head *bh;
-                        u32 block, offset;
-
-                        block = sbi->blockoffset;
-                        block += (sbi->sect_count - 2) >> (sb->s_blocksize_bits - 9);
-                        offset = ((sbi->sect_count - 2) << 9) & (sb->s_blocksize - 1);
-                        printk(KERN_DEBUG "hfs: backup: %u,%u,%u,%u\n",
-                                          sbi->blockoffset, sbi->sect_count,
-                                          block, offset);
-                        bh = sb_bread(sb, block);
-                        if (bh) {
-                                vhdr = (struct hfsplus_vh *)(bh->b_data + offset);
-                                if (be16_to_cpu(vhdr->signature) == HFSPLUS_VOLHEAD_SIG) {
-                                        memcpy(vhdr, sbi->s_vhdr, sizeof(*vhdr));
-                                        mark_buffer_dirty(bh);
-                                        brelse(bh);
-                                } else
-                                        printk(KERN_WARNING "hfs: backup not found!\n");
-                        }
-                }
+                memcpy(sbi->s_backup_vhdr, sbi->s_vhdr, sizeof(*sbi->s_vhdr));
+                write_backup = 1;
         }
+
+        error = hfsplus_submit_bio(sb->s_bdev,
+                                   sbi->part_start + HFSPLUS_VOLHEAD_SECTOR,
+                                   sbi->s_vhdr, WRITE_SYNC);
+        if (!write_backup)
+                goto out;
+
+        error2 = hfsplus_submit_bio(sb->s_bdev,
+                                  sbi->part_start + sbi->sect_count - 2,
+                                  sbi->s_backup_vhdr, WRITE_SYNC);
+        if (!error)
+                error2 = error;
+out:
         mutex_unlock(&sbi->alloc_mutex);
         mutex_unlock(&sbi->vh_mutex);
-        return 0;
+        return error;
 }
 
 static void hfsplus_write_super(struct super_block *sb)
@@ -229,7 +224,8 @@ static void hfsplus_put_super(struct super_block *sb)
         hfs_btree_close(sbi->ext_tree);
         iput(sbi->alloc_file);
         iput(sbi->hidden_dir);
-        brelse(sbi->s_vhbh);
+        kfree(sbi->s_vhdr);
+        kfree(sbi->s_backup_vhdr);
         unload_nls(sbi->nls);
         kfree(sb->s_fs_info);
         sb->s_fs_info = NULL;
diff --git a/fs/hfsplus/wrapper.c b/fs/hfsplus/wrapper.c
index 8972c20b3216..15e0eabb489e 100644
--- a/fs/hfsplus/wrapper.c
+++ b/fs/hfsplus/wrapper.c
@@ -24,6 +24,40 @@ struct hfsplus_wd {
         u16 embed_count;
 };
 
+static void hfsplus_end_io_sync(struct bio *bio, int err)
+{
+        if (err)
+                clear_bit(BIO_UPTODATE, &bio->bi_flags);
+        complete(bio->bi_private);
+}
+
+int hfsplus_submit_bio(struct block_device *bdev, sector_t sector,
+                void *data, int rw)
+{
+        DECLARE_COMPLETION_ONSTACK(wait);
+        struct bio *bio;
+
+        bio = bio_alloc(GFP_NOIO, 1);
+        bio->bi_sector = sector;
+        bio->bi_bdev = bdev;
+        bio->bi_end_io = hfsplus_end_io_sync;
+        bio->bi_private = &wait;
+
+        /*
+         * We always submit one sector at a time, so bio_add_page must not fail.
+         */
+        if (bio_add_page(bio, virt_to_page(data), HFSPLUS_SECTOR_SIZE,
+                         offset_in_page(data)) != HFSPLUS_SECTOR_SIZE)
+                BUG();
+
+        submit_bio(rw, bio);
+        wait_for_completion(&wait);
+
+        if (!bio_flagged(bio, BIO_UPTODATE))
+                return -EIO;
+        return 0;
+}
+
 static int hfsplus_read_mdb(void *bufptr, struct hfsplus_wd *wd)
 {
         u32 extent;
@@ -88,100 +122,111 @@ static int hfsplus_get_last_session(struct super_block *sb,
 int hfsplus_read_wrapper(struct super_block *sb)
 {
         struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
-        struct buffer_head *bh;
-        struct hfsplus_vh *vhdr;
         struct hfsplus_wd wd;
         sector_t part_start, part_size;
         u32 blocksize;
+        int error = 0;
 
+        error = -EINVAL;
         blocksize = sb_min_blocksize(sb, HFSPLUS_SECTOR_SIZE);
         if (!blocksize)
-                return -EINVAL;
+                goto out;