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authorChristoph Hellwig <hch@infradead.org>2011-05-04 18:55:15 +0000
committerAlex Elder <aelder@sgi.com>2011-05-24 11:17:22 -0500
commit55a7bc5a30ff2d30d8a34fea2af9fc601b32e61a (patch)
treea6cc677dc240ebfeec85b66a2669842dc3094461 /fs/xfs/xfs_ag.h
parente84661aa84e2e003738563f65155d4f12dc474e7 (diff)
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xfs: do not discard alloc btree blocks
Blocks for the allocation btree are allocated from and released to the AGFL, and thus frequently reused. Even worse we do not have an easy way to avoid using an AGFL block when it is discarded due to the simple FILO list of free blocks, and thus can frequently stall on blocks that are currently undergoing a discard. Add a flag to the busy extent tracking structure to skip the discard for allocation btree blocks. In normal operation these blocks are reused frequently enough that there is no need to discard them anyway, but if they spill over to the allocation btree as part of a balance we "leak" blocks that we would otherwise discard. We could fix this by adding another flag and keeping these block in the rbtree even after they aren't busy any more so that we could discard them when they migrate out of the AGFL. Given that this would cause significant overhead I don't think it's worthwile for now. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Alex Elder <aelder@sgi.com>
Diffstat (limited to 'fs/xfs/xfs_ag.h')
-rw-r--r--fs/xfs/xfs_ag.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index 8d52ba4..6530769 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -189,6 +189,7 @@ struct xfs_busy_extent {
xfs_extlen_t length;
unsigned int flags;
#define XFS_ALLOC_BUSY_DISCARDED 0x01 /* undergoing a discard op. */
+#define XFS_ALLOC_BUSY_SKIP_DISCARD 0x02 /* do not discard */
};
/*
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