diff options
Diffstat (limited to 'fs/xfs/libxfs/xfs_rmap_btree.c')
| -rw-r--r-- | fs/xfs/libxfs/xfs_rmap_btree.c | 45 |
1 files changed, 27 insertions, 18 deletions
diff --git a/fs/xfs/libxfs/xfs_rmap_btree.c b/fs/xfs/libxfs/xfs_rmap_btree.c index 1b48b7b3ee30..7388201e48d2 100644 --- a/fs/xfs/libxfs/xfs_rmap_btree.c +++ b/fs/xfs/libxfs/xfs_rmap_btree.c @@ -540,26 +540,35 @@ void xfs_rmapbt_compute_maxlevels( struct xfs_mount *mp) { - /* - * On a non-reflink filesystem, the maximum number of rmap - * records is the number of blocks in the AG, hence the max - * rmapbt height is log_$maxrecs($agblocks). However, with - * reflink each AG block can have up to 2^32 (per the refcount - * record format) owners, which means that theoretically we - * could face up to 2^64 rmap records. - * - * That effectively means that the max rmapbt height must be - * XFS_BTREE_MAXLEVELS. "Fortunately" we'll run out of AG - * blocks to feed the rmapbt long before the rmapbt reaches - * maximum height. The reflink code uses ag_resv_critical to - * disallow reflinking when less than 10% of the per-AG metadata - * block reservation since the fallback is a regular file copy. - */ - if (xfs_has_reflink(mp)) - mp->m_rmap_maxlevels = XFS_BTREE_MAXLEVELS; - else + if (!xfs_has_rmapbt(mp)) { + mp->m_rmap_maxlevels = 0; + return; + } + + if (xfs_has_reflink(mp)) { + /* + * Compute the asymptotic maxlevels for an rmap btree on a + * filesystem that supports reflink. + * + * On a reflink filesystem, each AG block can have up to 2^32 + * (per the refcount record format) owners, which means that + * theoretically we could face up to 2^64 rmap records. + * However, we're likely to run out of blocks in the AG long + * before that happens, which means that we must compute the + * max height based on what the btree will look like if it + * consumes almost all the blocks in the AG due to maximal + * sharing factor. + */ + mp->m_rmap_maxlevels = xfs_btree_space_to_height(mp->m_rmap_mnr, + mp->m_sb.sb_agblocks); + } else { + /* + * If there's no block sharing, compute the maximum rmapbt + * height assuming one rmap record per AG block. + */ mp->m_rmap_maxlevels = xfs_btree_compute_maxlevels( mp->m_rmap_mnr, mp->m_sb.sb_agblocks); + } } /* Calculate the refcount btree size for some records. */ |