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authorDarrick J. Wong <darrick.wong@oracle.com>2016-09-19 02:30:52 +0200
committerDave Chinner <david@fromorbit.com>2016-09-19 02:30:52 +0200
commit3fd129b63fd062a0d8f5d55994a6e98896c20fa7 (patch)
tree68012c248984b97daf6d535eb321f82abc595581 /fs/xfs/xfs_filestream.c
parentxfs: defer should allow ->finish_item to request a new transaction (diff)
downloadlinux-3fd129b63fd062a0d8f5d55994a6e98896c20fa7.tar.xz
linux-3fd129b63fd062a0d8f5d55994a6e98896c20fa7.zip
xfs: set up per-AG free space reservations
One unfortunate quirk of the reference count and reverse mapping btrees -- they can expand in size when blocks are written to *other* allocation groups if, say, one large extent becomes a lot of tiny extents. Since we don't want to start throwing errors in the middle of CoWing, we need to reserve some blocks to handle future expansion. The transaction block reservation counters aren't sufficient here because we have to have a reserve of blocks in every AG, not just somewhere in the filesystem. Therefore, create two per-AG block reservation pools. One feeds the AGFL so that rmapbt expansion always succeeds, and the other feeds all other metadata so that refcountbt expansion never fails. Use the count of how many reserved blocks we need to have on hand to create a virtual reservation in the AG. Through selective clamping of the maximum length of allocation requests and of the length of the longest free extent, we can make it look like there's less free space in the AG unless the reservation owner is asking for blocks. In other words, play some accounting tricks in-core to make sure that we always have blocks available. On the plus side, there's nothing to clean up if we crash, which is contrast to the strategy that the rough draft used (actually removing extents from the freespace btrees). Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Dave Chinner <dchinner@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs/xfs_filestream.c')
-rw-r--r--fs/xfs/xfs_filestream.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/fs/xfs/xfs_filestream.c b/fs/xfs/xfs_filestream.c
index 4a33a3304369..c8005fdaaa8a 100644
--- a/fs/xfs/xfs_filestream.c
+++ b/fs/xfs/xfs_filestream.c
@@ -30,6 +30,7 @@
#include "xfs_mru_cache.h"
#include "xfs_filestream.h"
#include "xfs_trace.h"
+#include "xfs_ag_resv.h"
struct xfs_fstrm_item {
struct xfs_mru_cache_elem mru;
@@ -198,7 +199,8 @@ xfs_filestream_pick_ag(
}
longest = xfs_alloc_longest_free_extent(mp, pag,
- xfs_alloc_min_freelist(mp, pag));
+ xfs_alloc_min_freelist(mp, pag),
+ xfs_ag_resv_needed(pag, XFS_AG_RESV_NONE));
if (((minlen && longest >= minlen) ||
(!minlen && pag->pagf_freeblks >= minfree)) &&
(!pag->pagf_metadata || !(flags & XFS_PICK_USERDATA) ||