xfs: improve handling of busy extents in the low-level allocator
Currently we force the log and simply try again if we hit a busy extent,
but especially with online discard enabled it might take a while after
the log force for the busy extents to disappear, and we might have
already completed our second pass.
So instead we add a new waitqueue and a generation counter to the pag
structure so that we can do wakeups once we've removed busy extents,
and we replace the single retry with an unconditional one - after
all we hold the AGF buffer lock, so no other allocations or frees
can be racing with us in this AG.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 7f351f7..20e2981 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -384,6 +384,8 @@
xfs_agino_t pagl_rightrec;
spinlock_t pagb_lock; /* lock for pagb_tree */
struct rb_root pagb_tree; /* ordered tree of busy extents */
+ unsigned int pagb_gen; /* generation count for pagb_tree */
+ wait_queue_head_t pagb_wait; /* woken when pagb_gen changes */
atomic_t pagf_fstrms; /* # of filestreams active in this AG */