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Commit 47062af8 authored by Josef Bacik's avatar Josef Bacik Committed by Greg Kroah-Hartman
Browse files

btrfs: properly report 0 avail for very full file systems 



commit 58bfe2ccec5f9f137b41dd38f335290dcc13cd5c upstream.

A user reported some issues with smaller file systems that get very
full.  While investigating this issue I noticed that df wasn't showing
100% full, despite having 0 chunk space and having < 1MiB of available
metadata space.

This turns out to be an overflow issue, we're doing:

  total_available_metadata_space - SZ_4M < global_block_rsv_size

to determine if there's not enough space to make metadata allocations,
which overflows if total_available_metadata_space is < 4M.  Fix this by
checking to see if our available space is greater than the 4M threshold.
This makes df properly report 100% usage on the file system.

CC: stable@vger.kernel.org # 4.14+
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent cf221a78

fs/btrfs/super.c

+1 −1
Original line number Diff line number Diff line
@@ -2135,7 +2135,7 @@ static int btrfs_statfs(struct dentry *dentry, struct kstatfs *buf) 
	 * calculated f_bavail.

	 */

	if (!mixed && block_rsv->space_info->full &&

	    total_free_meta - thresh < block_rsv->size)

	    (total_free_meta < thresh || total_free_meta - thresh < block_rsv->size))

		buf->f_bavail = 0;



	buf->f_type = BTRFS_SUPER_MAGIC;