linux-kernel - [PATCH 02/27] afs: Fix page overput in afs_fill

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Message-ID: <148908575583.16794.5285608492468338019.stgit@warthog.procyon.org.uk>
Date:   Thu, 09 Mar 2017 18:55:55 +0000
From:   David Howells <dhowells@...hat.com>
To:     viro@...IV.linux.org.uk
Cc:     Marc Dionne <marc.dionne@...istor.com>, dhowells@...hat.com,
        linux-fsdevel@...r.kernel.org, linux-afs@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 02/27] afs: Fix page overput in afs_fill_page()

afs_fill_page() loads the page it wants to fill into the afs_read request
without incrementing its refcount - but then calls afs_put_read() to clean
up afterwards, which then releases a ref on the page.

Fix this by getting a ref on the page before calling
afs_vnode_fetch_data().

This causes sync after a write to hang in afs_writepages_region() because
find_get_pages_tag() gets confused and doesn't return.

Fixes: 196ee9cd2d04 ("afs: Make afs_fs_fetch_data() take a list of pages")
Reported-by: Marc Dionne <marc.dionne@...istor.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Tested-by: Marc Dionne <marc.dionne@...istor.com>
---

 fs/afs/write.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/afs/write.c b/fs/afs/write.c
index e919e64cd4e0..3ac52f6a96ff 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -101,6 +101,7 @@ static int afs_fill_page(struct afs_vnode *vnode, struct key *key,
 	req->pos = pos;
 	req->nr_pages = 1;
 	req->pages[0] = page;
+	get_page(page);
 
 	i_size = i_size_read(&vnode->vfs_inode);
 	if (pos + PAGE_SIZE > i_size)