Commit 7833b865 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David Sterba
Browse files

btrfs: fix iomap_begin length for nocow writes 



can_nocow_extent can reduce the len passed in, which needs to be
propagated to btrfs_dio_iomap_begin so that iomap does not submit
more data then is mapped.

This problems exists since the btrfs_get_blocks_direct helper was added
in commit c5794e51 ("btrfs: Factor out write portion of
btrfs_get_blocks_direct"), but the ordered_extent splitting added in
commit b73a6fd1 ("btrfs: split partial dio bios before submit")
added a WARN_ON that made a syzkaller test fail.

Reported-by: default avatar <syzbot+ee90502d5c8fd1d0dd93@syzkaller.appspotmail.com>
Fixes: c5794e51 ("btrfs: Factor out write portion of btrfs_get_blocks_direct")
CC: stable@vger.kernel.org # 6.1+
Tested-by: default avatar <syzbot+ee90502d5c8fd1d0dd93@syzkaller.appspotmail.com>
Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 79b8ee70

fs/btrfs/inode.c

+12 −6
Original line number Diff line number Diff line
@@ -7264,7 +7264,7 @@ static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start, 
static int btrfs_get_blocks_direct_write(struct extent_map **map,

					 struct inode *inode,

					 struct btrfs_dio_data *dio_data,

					 u64 start, u64 len,

					 u64 start, u64 *lenp,

					 unsigned int iomap_flags)

{

	const bool nowait = (iomap_flags & IOMAP_NOWAIT);
@@ -7275,6 +7275,7 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map, 
	struct btrfs_block_group *bg;

	bool can_nocow = false;

	bool space_reserved = false;

	u64 len = *lenp;

	u64 prev_len;

	int ret = 0;
@@ -7345,15 +7346,19 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map, 
		free_extent_map(em);

		*map = NULL;



		if (nowait)

			return -EAGAIN;

		if (nowait) {

			ret = -EAGAIN;

			goto out;

		}



		/*

		 * If we could not allocate data space before locking the file

		 * range and we can't do a NOCOW write, then we have to fail.

		 */

		if (!dio_data->data_space_reserved)

			return -ENOSPC;

		if (!dio_data->data_space_reserved) {

			ret = -ENOSPC;

			goto out;

		}



		/*

		 * We have to COW and we have already reserved data space before,
@@ -7394,6 +7399,7 @@ static int btrfs_get_blocks_direct_write(struct extent_map **map, 
		btrfs_delalloc_release_extents(BTRFS_I(inode), len);

		btrfs_delalloc_release_metadata(BTRFS_I(inode), len, true);

	}

	*lenp = len;

	return ret;

}
@@ -7570,7 +7576,7 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start, 


	if (write) {

		ret = btrfs_get_blocks_direct_write(&em, inode, dio_data,

						    start, len, flags);

						    start, &len, flags);

		if (ret < 0)

			goto unlock_err;

		unlock_extents = true;