Btrfs: allow shrink_delalloc flush the needed reclaimed pages

Currently we only allow a maximum of 2 megabytes of pages to be flushed at a
time.  This was ok before, but now we have overcommit which will screw us in a
heartbeat if we are quickly filling the disk.  So instead pick either 2
megabytes or the number of pages we need to reclaim to be safe again, which ever
is larger.  Thanks,

Signed-off-by: Josef Bacik <josef@redhat.com>
(cherry picked from commit 877da174301dde9062b915da4c8103048be49702)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f828ce881e84faefcc4274a3b9a01b433bae0d11..fedbf86d1ec183242cac51cea7e9690e60be8c98 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3343,7 +3343,7 @@ static int shrink_delalloc(struct btrfs_trans_handle *trans,
        u64 max_reclaim;
        u64 reclaimed = 0;
        long time_left;
-       int nr_pages = (2 * 1024 * 1024) >> PAGE_CACHE_SHIFT;
+       unsigned long nr_pages = (2 * 1024 * 1024) >> PAGE_CACHE_SHIFT;
        int loops = 0;
        unsigned long progress;
 
@@ -3366,7 +3366,8 @@ static int shrink_delalloc(struct btrfs_trans_handle *trans,
        }
 
        max_reclaim = min(reserved, to_reclaim);
-
+       nr_pages = max_t(unsigned long, nr_pages,
+                        max_reclaim >> PAGE_CACHE_SHIFT);
        while (loops < 1024) {
                /* have the flusher threads jump in and do some IO */
                smp_mb();