xfs: add a shrinker to background inode reclaim

On low memory boxes or those with highmem, kernel can OOM before the
background reclaims inodes via xfssyncd. Add a shrinker to run inode
reclaim so that it inode reclaim is expedited when memory is low.

This is more complex than it needs to be because the VM folk don't
want a context added to the shrinker infrastructure. Hence we need
to add a global list of XFS mount structures so the shrinker can
traverse them.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/xfs/xfs_ag.h b/fs/xfs/xfs_ag.h
index b1a5a1ff88ea..abb8222b88c9 100644
--- a/fs/xfs/xfs_ag.h
+++ b/fs/xfs/xfs_ag.h
@@ -223,6 +223,7 @@ typedef struct xfs_perag {
         int             pag_ici_init;   /* incore inode cache initialised */
         rwlock_t        pag_ici_lock;   /* incore inode lock */
         struct radix_tree_root pag_ici_root;    /* incore inode cache root */
+        int             pag_ici_reclaimable;    /* reclaimable inodes */
 #endif
         int             pagb_count;     /* pagb slots in use */
         xfs_perag_busy_t pagb_list[XFS_PAGB_NUM_SLOTS]; /* unstable blocks */