ceph: fix readpage from fscache

ceph_readpage() unlocks page prematurely prematurely in the case
that page is reading from fscache. Caller of readpage expects that
page is uptodate when it get unlocked. So page shoule get locked
by completion callback of fscache_read_or_alloc_pages()

Cc: stable@vger.kernel.org # 4.1+, needs backporting for < 4.7
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

1 files changed, 15 insertions, 9 deletions

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 50836280a6f8..1bc709fe330a 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -189,7 +189,7 @@ static int ceph_releasepage(struct page *page, gfp_t g)
 /*
  * read a single page, without unlocking it.
  */
-static int readpage_nounlock(struct file *filp, struct page *page)
+static int ceph_do_readpage(struct file *filp, struct page *page)
 {
         struct inode *inode = file_inode(filp);
         struct ceph_inode_info *ci = ceph_inode(inode);
@@ -219,7 +219,7 @@ static int readpage_nounlock(struct file *filp, struct page *page)
 
         err = ceph_readpage_from_fscache(inode, page);
         if (err == 0)
-                goto out;
+                return -EINPROGRESS;
 
         dout("readpage inode %p file %p page %p index %lu\n",
              inode, filp, page, page->index);
@@ -249,8 +249,11 @@ out:
 
 static int ceph_readpage(struct file *filp, struct page *page)
 {
-        int r = readpage_nounlock(filp, page);
-        unlock_page(page);
+        int r = ceph_do_readpage(filp, page);
+        if (r != -EINPROGRESS)
+                unlock_page(page);
+        else
+                r = 0;
         return r;
 }
 
@@ -1237,7 +1240,7 @@ retry_locked:
                         goto retry_locked;
                 r = writepage_nounlock(page, NULL);
                 if (r < 0)
-                        goto fail_nosnap;
+                        goto fail_unlock;
                 goto retry_locked;
         }
 
@@ -1265,11 +1268,14 @@ retry_locked:
         }
 
         /* we need to read it. */
-        r = readpage_nounlock(file, page);
-        if (r < 0)
-                goto fail_nosnap;
+        r = ceph_do_readpage(file, page);
+        if (r < 0) {
+                if (r == -EINPROGRESS)
+                        return -EAGAIN;
+                goto fail_unlock;
+        }
         goto retry_locked;
-fail_nosnap:
+fail_unlock:
         unlock_page(page);
         return r;
 }