4 files changed, 21 insertions, 8 deletions

diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index dcb3e1d5dbf6..88a48ccb7d9e 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -200,6 +200,7 @@ extern atomic_t fscache_n_store_vmscan_not_storing;
 extern atomic_t fscache_n_store_vmscan_gone;
 extern atomic_t fscache_n_store_vmscan_busy;
 extern atomic_t fscache_n_store_vmscan_cancelled;
+extern atomic_t fscache_n_store_vmscan_wait;
 
 extern atomic_t fscache_n_marks;
 extern atomic_t fscache_n_uncaches;
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 4dbbca162620..f9b2fb3ae492 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -56,6 +56,7 @@ bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
 
         _enter("%p,%p,%x", cookie, page, gfp);
 
+try_again:
         rcu_read_lock();
         val = radix_tree_lookup(&cookie->stores, page->index);
         if (!val) {
@@ -104,11 +105,19 @@ bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
         return true;
 
 page_busy:
-        /* we might want to wait here, but that could deadlock the allocator as
-         * the work threads writing to the cache may all end up sleeping
-         * on memory allocation */
-        fscache_stat(&fscache_n_store_vmscan_busy);
-        return false;
+        /* We will wait here if we're allowed to, but that could deadlock the
+         * allocator as the work threads writing to the cache may all end up
+         * sleeping on memory allocation, so we may need to impose a timeout
+         * too. */
+        if (!(gfp & __GFP_WAIT)) {
+                fscache_stat(&fscache_n_store_vmscan_busy);
+                return false;
+        }
+
+        fscache_stat(&fscache_n_store_vmscan_wait);
+        __fscache_wait_on_page_write(cookie, page);
+        gfp &= ~__GFP_WAIT;
+        goto try_again;
 }
 EXPORT_SYMBOL(__fscache_maybe_release_page);
 
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 51cdaee14109..8179e8bc4a3d 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -69,6 +69,7 @@ atomic_t fscache_n_store_vmscan_not_storing;
 atomic_t fscache_n_store_vmscan_gone;
 atomic_t fscache_n_store_vmscan_busy;
 atomic_t fscache_n_store_vmscan_cancelled;
+atomic_t fscache_n_store_vmscan_wait;
 
 atomic_t fscache_n_marks;
 atomic_t fscache_n_uncaches;
@@ -232,11 +233,12 @@ static int fscache_stats_show(struct seq_file *m, void *v)
                    atomic_read(&fscache_n_store_radix_deletes),
                    atomic_read(&fscache_n_store_pages_over_limit));
 
-        seq_printf(m, "VmScan : nos=%u gon=%u bsy=%u can=%u\n",
+        seq_printf(m, "VmScan : nos=%u gon=%u bsy=%u can=%u wt=%u\n",
                    atomic_read(&fscache_n_store_vmscan_not_storing),
                    atomic_read(&fscache_n_store_vmscan_gone),
                    atomic_read(&fscache_n_store_vmscan_busy),
-                   atomic_read(&fscache_n_store_vmscan_cancelled));
+                   atomic_read(&fscache_n_store_vmscan_cancelled),
+                   atomic_read(&fscache_n_store_vmscan_wait));
 
         seq_printf(m, "Ops    : pend=%u run=%u enq=%u can=%u rej=%u\n",
                    atomic_read(&fscache_n_op_pend),
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 5209916e1222..b673be31590e 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -1794,7 +1794,8 @@ int nfs_migrate_page(struct address_space *mapping, struct page *newpage,
         if (PagePrivate(page))
                 return -EBUSY;
 
-        nfs_fscache_release_page(page, GFP_KERNEL);
+        if (!nfs_fscache_release_page(page, GFP_KERNEL))
+                return -EBUSY;
 
         return migrate_page(mapping, newpage, page, mode);
 }