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>

1 files changed, 104 insertions, 59 deletions

diff --git a/fs/hfsplus/wrapper.c b/fs/hfsplus/wrapper.c
index 8972c20..15e0eab 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;
 
 	if (hfsplus_get_last_session(sb, &part_start, &part_size))
-		return -EINVAL;
+		goto out;
 	if ((u64)part_start + part_size > 0x100000000ULL) {
 		pr_err("hfs: volumes larger than 2TB are not supported yet\n");
-		return -EINVAL;
+		goto out;
 	}
-	while (1) {
-		bh = sb_bread512(sb, part_start + HFSPLUS_VOLHEAD_SECTOR, vhdr);
-		if (!bh)
-			return -EIO;
-
-		if (vhdr->signature == cpu_to_be16(HFSP_WRAP_MAGIC)) {
-			if (!hfsplus_read_mdb(vhdr, &wd))
-				goto error;
-			wd.ablk_size >>= HFSPLUS_SECTOR_SHIFT;
-			part_start += wd.ablk_start + wd.embed_start * wd.ablk_size;
-			part_size = wd.embed_count * wd.ablk_size;
-			brelse(bh);
-			bh = sb_bread512(sb, part_start + HFSPLUS_VOLHEAD_SECTOR, vhdr);
-			if (!bh)
-				return -EIO;
-		}
-		if (vhdr->signature == cpu_to_be16(HFSPLUS_VOLHEAD_SIG))
-			break;
-		if (vhdr->signature == cpu_to_be16(HFSPLUS_VOLHEAD_SIGX)) {
-			set_bit(HFSPLUS_SB_HFSX, &sbi->flags);
-			break;
-		}
-		brelse(bh);
 
-		/* check for a partition block
+	error = -ENOMEM;
+	sbi->s_vhdr = kmalloc(HFSPLUS_SECTOR_SIZE, GFP_KERNEL);
+	if (!sbi->s_vhdr)
+		goto out;
+	sbi->s_backup_vhdr = kmalloc(HFSPLUS_SECTOR_SIZE, GFP_KERNEL);
+	if (!sbi->s_backup_vhdr)
+		goto out_free_vhdr;
+
+reread:
+	error = hfsplus_submit_bio(sb->s_bdev,
+				   part_start + HFSPLUS_VOLHEAD_SECTOR,
+				   sbi->s_vhdr, READ);
+	if (error)
+		goto out_free_backup_vhdr;
+
+	error = -EINVAL;
+	switch (sbi->s_vhdr->signature) {
+	case cpu_to_be16(HFSPLUS_VOLHEAD_SIGX):
+		set_bit(HFSPLUS_SB_HFSX, &sbi->flags);
+		/*FALLTHRU*/
+	case cpu_to_be16(HFSPLUS_VOLHEAD_SIG):
+		break;
+	case cpu_to_be16(HFSP_WRAP_MAGIC):
+		if (!hfsplus_read_mdb(sbi->s_vhdr, &wd))
+			goto out;
+		wd.ablk_size >>= HFSPLUS_SECTOR_SHIFT;
+		part_start += wd.ablk_start + wd.embed_start * wd.ablk_size;
+		part_size = wd.embed_count * wd.ablk_size;
+		goto reread;
+	default:
+		/*
+		 * Check for a partition block.
+		 *
 		 * (should do this only for cdrom/loop though)
 		 */
 		if (hfs_part_find(sb, &part_start, &part_size))
-			return -EINVAL;
+			goto out;
+		goto reread;
+	}
+
+	error = hfsplus_submit_bio(sb->s_bdev,
+				   part_start + part_size - 2,
+				   sbi->s_backup_vhdr, READ);
+	if (error)
+		goto out_free_backup_vhdr;
+
+	error = -EINVAL;
+	if (sbi->s_backup_vhdr->signature != sbi->s_vhdr->signature) {
+		printk(KERN_WARNING
+			"hfs: invalid secondary volume header\n");
+		goto out_free_backup_vhdr;
 	}
 
-	blocksize = be32_to_cpu(vhdr->blocksize);
-	brelse(bh);
+	blocksize = be32_to_cpu(sbi->s_vhdr->blocksize);
 
-	/* block size must be at least as large as a sector
-	 * and a multiple of 2
+	/*
+	 * Block size must be at least as large as a sector and a multiple of 2.
 	 */
-	if (blocksize < HFSPLUS_SECTOR_SIZE ||
-	    ((blocksize - 1) & blocksize))
-		return -EINVAL;
+	if (blocksize < HFSPLUS_SECTOR_SIZE || ((blocksize - 1) & blocksize))
+		goto out_free_backup_vhdr;
 	sbi->alloc_blksz = blocksize;
 	sbi->alloc_blksz_shift = 0;
 	while ((blocksize >>= 1) != 0)
 		sbi->alloc_blksz_shift++;
 	blocksize = min(sbi->alloc_blksz, (u32)PAGE_SIZE);
 
-	/* align block size to block offset */
+	/*
+	 * Align block size to block offset.
+	 */
 	while (part_start & ((blocksize >> HFSPLUS_SECTOR_SHIFT) - 1))
 		blocksize >>= 1;
 
 	if (sb_set_blocksize(sb, blocksize) != blocksize) {
 		printk(KERN_ERR "hfs: unable to set blocksize to %u!\n", blocksize);
-		return -EINVAL;
+		goto out_free_backup_vhdr;
 	}
 
 	sbi->blockoffset =
 		part_start >> (sb->s_blocksize_bits - HFSPLUS_SECTOR_SHIFT);
+	sbi->part_start = part_start;
 	sbi->sect_count = part_size;
 	sbi->fs_shift = sbi->alloc_blksz_shift - sb->s_blocksize_bits;
-
-	bh = sb_bread512(sb, part_start + HFSPLUS_VOLHEAD_SECTOR, vhdr);
-	if (!bh)
-		return -EIO;
-
-	/* should still be the same... */
-	if (test_bit(HFSPLUS_SB_HFSX, &sbi->flags)) {
-		if (vhdr->signature != cpu_to_be16(HFSPLUS_VOLHEAD_SIGX))
-			goto error;
-	} else {
-		if (vhdr->signature != cpu_to_be16(HFSPLUS_VOLHEAD_SIG))
-			goto error;
-	}
-
-	sbi->s_vhbh = bh;
-	sbi->s_vhdr = vhdr;
-
 	return 0;
- error:
-	brelse(bh);
-	return -EINVAL;
+
+out_free_backup_vhdr:
+	kfree(sbi->s_backup_vhdr);
+out_free_vhdr:
+	kfree(sbi->s_vhdr);
+out:
+	return error;
 }