Patch "f2fs: hide a maybe-uninitialized warning" has been added to the 4.9-stable tree

Patch "f2fs: hide a maybe-uninitialized warning" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    f2fs: hide a maybe-uninitialized warning

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     f2fs-hide-a-maybe-uninitialized-warning.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 230436b3ef3fd7d4a1da19edf5e87bb2d74e0fc2 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>
Date: Wed, 2 Nov 2016 14:52:15 +0100
Subject: f2fs: hide a maybe-uninitialized warning
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

From: Arnd Bergmann <arnd@arndb.de>

commit 230436b3ef3fd7d4a1da19edf5e87bb2d74e0fc2 upstream.

gcc is unsure about the use of last_ofs_in_node, which might happen
without a prior initialization:

fs/f2fs//git/arm-soc/fs/f2fs/data.c: In function ‘f2fs_map_blocks’:
fs/f2fs/data.c:799:54: warning: ‘last_ofs_in_node’ may be used uninitialized in this function [-Wmaybe-uninitialized]
   if (prealloc && dn.ofs_in_node != last_ofs_in_node + 1) {

As pointed out by Chao Yu, the code is actually correct as 'prealloc'
is only set if the last_ofs_in_node has been set, the two always
get updated together.

This initializes last_ofs_in_node to dn.ofs_in_node for each
new dnode at the start of the 'next_block' loop, which at that
point is a correct initialization as well. I assume that compilers
that correctly track the contents of the variables and do not
warn about the condition also figure out that they can eliminate
the extra assignment here.

Fixes: 46008c6d4232 ("f2fs: support in batch multi blocks preallocation")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/f2fs/data.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -716,7 +716,7 @@ next_dnode:
 	}
 
 	prealloc = 0;
-	ofs_in_node = dn.ofs_in_node;
+	last_ofs_in_node = ofs_in_node = dn.ofs_in_node;
 	end_offset = ADDRS_PER_PAGE(dn.node_page, inode);
 
 next_block:


Patches currently in stable-queue which might be from arnd@arndb.de are

queue-4.9/asoc-lpass-platform-initialize-dma-channel-number.patch
queue-4.9/scsi-mvsas-fix-command_active-typo.patch
queue-4.9/debugfs-improve-define_debugfs_attribute-for-config_debug_fs.patch
queue-4.9/f2fs-hide-a-maybe-uninitialized-warning.patch