diff options
Diffstat (limited to 'fs/xfs/xfs_alloc.h')
| -rw-r--r-- | fs/xfs/xfs_alloc.h | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h index 0ab56b32c7eb..d0b3bc72005b 100644 --- a/fs/xfs/xfs_alloc.h +++ b/fs/xfs/xfs_alloc.h @@ -75,6 +75,22 @@ typedef unsigned int xfs_alloctype_t; #define XFS_ALLOC_SET_ASIDE(mp) (4 + ((mp)->m_sb.sb_agcount * 4)) /* + * When deciding how much space to allocate out of an AG, we limit the + * allocation maximum size to the size the AG. However, we cannot use all the + * blocks in the AG - some are permanently used by metadata. These + * blocks are generally: + * - the AG superblock, AGF, AGI and AGFL + * - the AGF (bno and cnt) and AGI btree root blocks + * - 4 blocks on the AGFL according to XFS_ALLOC_SET_ASIDE() limits + * + * The AG headers are sector sized, so the amount of space they take up is + * dependent on filesystem geometry. The others are all single blocks. + */ +#define XFS_ALLOC_AG_MAX_USABLE(mp) \ + ((mp)->m_sb.sb_agblocks - XFS_BB_TO_FSB(mp, XFS_FSS_TO_BB(mp, 4)) - 7) + + +/* * Argument structure for xfs_alloc routines. * This is turned into a structure to avoid having 20 arguments passed * down several levels of the stack. |