From dd2bc473482eedc60c29cf00ad12568ce40ce511 Mon Sep 17 00:00:00 2001
From: "Yan, Zheng" <zyan@redhat.com>
Date: Fri, 4 Aug 2017 11:22:31 +0800
Subject: [PATCH] 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>
---
 fs/ceph/addr.c  | 24 +++++++++++++++---------
 fs/ceph/cache.c | 12 +++---------
 2 files changed, 18 insertions(+), 18 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;
 }
diff --git a/fs/ceph/cache.c b/fs/ceph/cache.c
index fd1172823f86..337f88673ed9 100644
--- a/fs/ceph/cache.c
+++ b/fs/ceph/cache.c
@@ -297,13 +297,7 @@ void ceph_fscache_file_set_cookie(struct inode *inode, struct file *filp)
 	}
 }
 
-static void ceph_vfs_readpage_complete(struct page *page, void *data, int error)
-{
-	if (!error)
-		SetPageUptodate(page);
-}
-
-static void ceph_vfs_readpage_complete_unlock(struct page *page, void *data, int error)
+static void ceph_readpage_from_fscache_complete(struct page *page, void *data, int error)
 {
 	if (!error)
 		SetPageUptodate(page);
@@ -331,7 +325,7 @@ int ceph_readpage_from_fscache(struct inode *inode, struct page *page)
 		return -ENOBUFS;
 
 	ret = fscache_read_or_alloc_page(ci->fscache, page,
-					 ceph_vfs_readpage_complete, NULL,
+					 ceph_readpage_from_fscache_complete, NULL,
 					 GFP_KERNEL);
 
 	switch (ret) {
@@ -360,7 +354,7 @@ int ceph_readpages_from_fscache(struct inode *inode,
 		return -ENOBUFS;
 
 	ret = fscache_read_or_alloc_pages(ci->fscache, mapping, pages, nr_pages,
-					  ceph_vfs_readpage_complete_unlock,
+					  ceph_readpage_from_fscache_complete,
 					  NULL, mapping_gfp_mask(mapping));
 
 	switch (ret) {