xfs: reduce metafile reservations

There is no point in reserving more space than actually available
on the data device for the worst case scenario that is unlikely to
happen.  Reserve at most 1/4th of the data device blocks, which is
still a heuristic.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>

diff --git a/fs/xfs/libxfs/xfs_metafile.c b/fs/xfs/libxfs/xfs_metafile.c
index 88f011750add5c4efc7298a5ddfa5b6310d3c78d..225923e463c41e39feceb740c781c06c8acdd6cc 100644 (file)
--- a/fs/xfs/libxfs/xfs_metafile.c
+++ b/fs/xfs/libxfs/xfs_metafile.c
@@ -260,6 +260,7 @@ xfs_metafile_resv_init(
        struct xfs_rtgroup      *rtg = NULL;
        xfs_filblks_t           used = 0, target = 0;
        xfs_filblks_t           hidden_space;
+       xfs_rfsblock_t          dblocks_avail = mp->m_sb.sb_dblocks / 4;
        int                     error = 0;
 
        if (!xfs_has_metadir(mp))
@@ -297,6 +298,8 @@ xfs_metafile_resv_init(
         */
        if (used > target)
                target = used;
+       else if (target > dblocks_avail)
+               target = dblocks_avail;
        hidden_space = target - used;
 
        error = xfs_dec_fdblocks(mp, hidden_space, true);