mm: make read_cache_page synchronous

Ensure pages are uptodate after returning from read_cache_page, which allows
us to cut out most of the filesystem-internal PageUptodate calls.

I didn't have a great look down the call chains, but this appears to fixes 7
possible use-before uptodate in hfs, 2 in hfsplus, 1 in jfs, a few in
ecryptfs, 1 in jffs2, and a possible cleared data overwritten with readpage in
block2mtd.  All depending on whether the filler is async and/or can return
with a !uptodate page.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 7 deletions

diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
index b905ae37f912..034fcfd4e330 100644
--- a/fs/afs/mntpt.c
+++ b/fs/afs/mntpt.c
@@ -68,13 +68,11 @@ int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
         }
 
         ret = -EIO;
-        wait_on_page_locked(page);
-        buf = kmap(page);
-        if (!PageUptodate(page))
-                goto out_free;
         if (PageError(page))
                 goto out_free;
 
+        buf = kmap(page);
+
         /* examine the symlink's contents */
         size = vnode->status.size;
         _debug("symlink to %*.*s", (int) size, (int) size, buf);
@@ -91,8 +89,8 @@ int afs_mntpt_check_symlink(struct afs_vnode *vnode, struct key *key)
 
         ret = 0;
 
-out_free:
         kunmap(page);
+out_free:
         page_cache_release(page);
 out:
         _leave(" = %d", ret);
@@ -171,8 +169,7 @@ static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
         }
 
         ret = -EIO;
-        wait_on_page_locked(page);
-        if (!PageUptodate(page) || PageError(page))
+        if (PageError(page))
                 goto error;
 
         buf = kmap(page);