path: root/fs/xfs/libxfs/xfs_rmap_btree.h
diff options
authorDarrick J. Wong <darrick.wong@oracle.com>2016-10-03 09:11:44 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2016-10-05 16:26:27 -0700
commit84d6961910ea7b3ae8d8338f5b4df25dea68cee9 (patch)
treef9c9c9f6f34bce9ff3b035df350cfe70e16b24f1 /fs/xfs/libxfs/xfs_rmap_btree.h
parentf7ca35227253dc8244fd908140b06010e67a31e5 (diff)
xfs: preallocate blocks for worst-case btree expansion
To gracefully handle the situation where a CoW operation turns a single refcount extent into a lot of tiny ones and then run out of space when a tree split has to happen, use the per-AG reserved block pool to pre-allocate all the space we'll ever need for a maximal btree. For a 4K block size, this only costs an overhead of 0.3% of available disk space. When reflink is enabled, we have an unfortunate problem with rmap -- since we can share a block billions of times, this means that the reverse mapping btree can expand basically infinitely. When an AG is so full that there are no free blocks with which to expand the rmapbt, the filesystem will shut down hard. This is rather annoying to the user, so use the AG reservation code to reserve a "reasonable" amount of space for rmap. We'll prevent reflinks and CoW operations if we think we're getting close to exhausting an AG's free space rather than shutting down, but this permanent reservation should be enough for "most" users. Hopefully. Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> [hch@lst.de: ensure that we invalidate the freed btree buffer] Signed-off-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'fs/xfs/libxfs/xfs_rmap_btree.h')
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/xfs/libxfs/xfs_rmap_btree.h b/fs/xfs/libxfs/xfs_rmap_btree.h
index e73a55357dab..2a9ac472fb15 100644
--- a/fs/xfs/libxfs/xfs_rmap_btree.h
+++ b/fs/xfs/libxfs/xfs_rmap_btree.h
@@ -58,4 +58,11 @@ struct xfs_btree_cur *xfs_rmapbt_init_cursor(struct xfs_mount *mp,
int xfs_rmapbt_maxrecs(struct xfs_mount *mp, int blocklen, int leaf);
extern void xfs_rmapbt_compute_maxlevels(struct xfs_mount *mp);
+extern xfs_extlen_t xfs_rmapbt_calc_size(struct xfs_mount *mp,
+ unsigned long long len);
+extern xfs_extlen_t xfs_rmapbt_max_size(struct xfs_mount *mp);
+extern int xfs_rmapbt_calc_reserves(struct xfs_mount *mp,
+ xfs_agnumber_t agno, xfs_extlen_t *ask, xfs_extlen_t *used);
#endif /* __XFS_RMAP_BTREE_H__ */