nobh: nobh_write_end fix

This path mustn't have been tested :( I did attempt to exercise it
by injecting failures here, but I suspect PageMappedToDisk may have
been getting in the way. Will need more of a look, although I think
nobh mode is OK for an -rc1 (it shouldn't eat anyone's data).

Commit 03158cd7eb3374843de68421142ca5900df845d9 ("fs: restore nobh")
introcduced a NULL deref.  Spotted by the Coverity checker.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/buffer.c b/fs/buffer.c
index 76403b1..7249e01 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2563,7 +2563,7 @@ int nobh_write_end(struct file *file, struct address_space *mapping,
                        struct page *page, void *fsdata)
 {
        struct inode *inode = page->mapping->host;
-       struct buffer_head *head = NULL;
+       struct buffer_head *head = fsdata;
        struct buffer_head *bh;
 
        if (!PageMappedToDisk(page)) {
@@ -2584,7 +2584,6 @@ int nobh_write_end(struct file *file, struct address_space *mapping,
        unlock_page(page);
        page_cache_release(page);
 
-       head = fsdata;
        while (head) {
                bh = head;
                head = head->b_this_page;