Btrfs: deal with errors in write_dev_supers (634554dc) · Commits · 戴 / test

If you try to mount -o loop a restored file system it will panic if the file ends up being smaller than the original disk. This is because we go to try and get a block for a super that may be past the EOF which makes __getblk return NULL for a buffer head when we aren't expecting it to. Fix this by dealing with this case and just jacking up the errors count. With this patch we no longer panic when mounting a restored file system loopback. Thanks, Signed-off-by:

Josef Bacik <jbacik@fusionio.com>

fs/btrfs/disk-io.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -2986,7 +2986,10 @@ static int write_dev_supers(struct btrfs_device *device,
		if (wait) {
		bh = __find_get_block(device->bdev, bytenr / 4096,
		BTRFS_SUPER_INFO_SIZE);
		BUG_ON(!bh);
		if (!bh) {
		errors++;
		continue;
		}
		wait_on_buffer(bh);
		if (!buffer_uptodate(bh))
		errors++;
		@@ -3013,6 +3016,13 @@ static int write_dev_supers(struct btrfs_device *device,
		*/
		bh = __getblk(device->bdev, bytenr / 4096,
		BTRFS_SUPER_INFO_SIZE);
		if (!bh) {
		printk(KERN_ERR "btrfs: couldn't get super "
		"buffer head for bytenr %Lu\n", bytenr);
		errors++;
		continue;
		}

		memcpy(bh->b_data, sb, BTRFS_SUPER_INFO_SIZE);

		/* one reference for submit_bh */

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