3 files changed, 54 insertions, 1 deletions

diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index ce84ffd0264c..31e90335b83d 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -35,6 +35,7 @@
 #include "xfs_error.h"
 #include "xfs_trace.h"
 
+struct workqueue_struct *xfs_alloc_wq;
 
 #define XFS_ABSDIFF(a,b)        (((a) <= (b)) ? ((b) - (a)) : ((a) - (b)))
 
@@ -2207,7 +2208,7 @@ xfs_alloc_read_agf(
  * group or loop over the allocation groups to find the result.
  */
 int                             /* error */
-xfs_alloc_vextent(
+__xfs_alloc_vextent(
         xfs_alloc_arg_t *args)  /* allocation argument structure */
 {
         xfs_agblock_t   agsize; /* allocation group size */
@@ -2417,6 +2418,37 @@ error0:
         return error;
 }
 
+static void
+xfs_alloc_vextent_worker(
+        struct work_struct      *work)
+{
+        struct xfs_alloc_arg    *args = container_of(work,
+                                                struct xfs_alloc_arg, work);
+        unsigned long           pflags;
+
+        /* we are in a transaction context here */
+        current_set_flags_nested(&pflags, PF_FSTRANS);
+
+        args->result = __xfs_alloc_vextent(args);
+        complete(args->done);
+
+        current_restore_flags_nested(&pflags, PF_FSTRANS);
+}
+
+
+int                             /* error */
+xfs_alloc_vextent(
+        xfs_alloc_arg_t *args)  /* allocation argument structure */
+{
+        DECLARE_COMPLETION_ONSTACK(done);
+
+        args->done = &done;
+        INIT_WORK(&args->work, xfs_alloc_vextent_worker);
+        queue_work(xfs_alloc_wq, &args->work);
+        wait_for_completion(&done);
+        return args->result;
+}
+
 /*
  * Free an extent.
  * Just break up the extent address and hand off to xfs_free_ag_extent
diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h
index 2f52b924be79..ab5d0fd2f535 100644
--- a/fs/xfs/xfs_alloc.h
+++ b/fs/xfs/xfs_alloc.h
@@ -25,6 +25,8 @@ struct xfs_perag;
 struct xfs_trans;
 struct xfs_busy_extent;
 
+extern struct workqueue_struct *xfs_alloc_wq;
+
 /*
  * Freespace allocation types.  Argument to xfs_alloc_[v]extent.
  */
@@ -119,6 +121,9 @@ typedef struct xfs_alloc_arg {
         char            isfl;           /* set if is freelist blocks - !acctg */
         char            userdata;       /* set if this is user data */
         xfs_fsblock_t   firstblock;     /* io first block allocated */
+        struct completion *done;
+        struct work_struct work;
+        int             result;
 } xfs_alloc_arg_t;
 
 /*
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 06d23b976f4c..5484888d39c4 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1607,12 +1607,28 @@ xfs_init_workqueues(void)
         xfs_syncd_wq = alloc_workqueue("xfssyncd", WQ_NON_REENTRANT, 0);
         if (!xfs_syncd_wq)
                 return -ENOMEM;
+
+        /*
+         * The allocation workqueue can be used in memory reclaim situations
+         * (writepage path), and parallelism is only limited by the number of
+         * AGs in all the filesystems mounted. Hence use the default large
+         * max_active value for this workqueue.
+         */
+        xfs_alloc_wq = alloc_workqueue("xfsalloc", WQ_MEM_RECLAIM, 0);
+        if (!xfs_alloc_wq)
+                goto out_destroy_syncd;
+
         return 0;
+
+out_destroy_syncd:
+        destroy_workqueue(xfs_syncd_wq);
+        return -ENOMEM;
 }
 
 STATIC void
 xfs_destroy_workqueues(void)
 {
+        destroy_workqueue(xfs_alloc_wq);
         destroy_workqueue(xfs_syncd_wq);
 }