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authorDave Chinner <david@fromorbit.com>2015-02-23 13:22:03 +0300
committerDave Chinner <david@fromorbit.com>2015-02-23 13:22:03 +0300
commit0d485ada404b3614b045e574bec26aaf5d9b3c5b (patch)
treeb08812daee1eed9e8be59e6c12bf0eeef5b6f7cf /fs/xfs/xfs_iomap.c
parente88b64ea1f3da64dbb52636377be295c90367377 (diff)
downloadlinux-0d485ada404b3614b045e574bec26aaf5d9b3c5b.tar.xz
xfs: use generic percpu counters for free block counter
XFS has hand-rolled per-cpu counters for the superblock since before there was any generic implementation. The free block counter is special in that it is used for ENOSPC detection outside transaction contexts for for delayed allocation. This means that the counter needs to be accurate at zero. The current per-cpu counter code jumps through lots of hoops to ensure we never run past zero, but we don't need to make all those jumps with the generic counter implementation. The generic counter implementation allows us to pass a "batch" threshold at which the addition/subtraction to the counter value will be folded back into global value under lock. We can use this feature to reduce the batch size as we approach 0 in a very similar manner to the existing counters and their rebalance algorithm. If we use a batch size of 1 as we approach 0, then every addition and subtraction will be done against the global value and hence allow accurate detection of zero threshold crossing. Hence we can replace the handrolled, accurate-at-zero counters with generic percpu counters. Note: this removes just enough of the icsb infrastructure to compile without warnings. The rest will go in subsequent commits. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Brian Foster <bfoster@redhat.com> Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs/xfs_iomap.c')
-rw-r--r--fs/xfs/xfs_iomap.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index ccb1dd0d509e..205b948c9d20 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -461,7 +461,7 @@ xfs_iomap_prealloc_size(
alloc_blocks);
xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
- freesp = mp->m_sb.sb_fdblocks;
+ freesp = percpu_counter_read_positive(&mp->m_fdblocks);
if (freesp < mp->m_low_space[XFS_LOWSP_5_PCNT]) {
shift = 2;
if (freesp < mp->m_low_space[XFS_LOWSP_4_PCNT])