Re: [GIT PULL for v7.1] vfs fixes

[David Howells]

Nathan Chancellor <nathan@xxxxxxxxxx> wrote:

> > David Howells (22):
> >       netfs: Fix potential for tearing in ->remote_i_size and ->zero_point
> ...
> >  fs/smb/client/cifsfs.c       |  38 ++++--
> 
> The changes in this file from that patch breaks the build with clang:
> 
>   fs/smb/client/cifsfs.c:1390:29: error: variable 'old_size' is uninitialized when used here [-Werror,-Wuninitialized]
>    1390 |                 if (rc == 0 && new_size > old_size) {
>         |                                           ^~~~~~~~
>   fs/smb/client/cifsfs.c:1307:37: note: initialize the variable 'old_size' to silence this warning
>    1307 |         unsigned long long i_size, old_size, new_size, zero_point;
>         |                                            ^
>         |                                             = 0
>   fs/smb/client/cifsfs.c:1375:13: error: variable 'zero_point' is uninitialized when used here [-Werror,-Wuninitialized]
>    1375 |         if (fend > zero_point)
>         |                    ^~~~~~~~~~
>   fs/smb/client/cifsfs.c:1307:59: note: initialize the variable 'zero_point' to silence this warning
>    1307 |         unsigned long long i_size, old_size, new_size, zero_point;
>         |                                                                  ^
>         |                                                                   = 0
>   2 errors generated.

For some reason, make W=1 with gcc doesn't seem to generate uninitialised
variable warnings (though maybe clang does?).  Is that specifically
suppressed?

	ifdef CONFIG_CC_IS_GCC
	KBUILD_CFLAGS += -Wno-maybe-uninitialized
	endif

I guess.  Can we remove that?

> There were no -next updates last week, so it seems like the majority of
> this pull request saw zero -next testing time. I see two kbuild test
> robot build reports but I guess they were ignored.
> 
>   https://lore.kernel.org/202605031459.eX5UbO3K-lkp@xxxxxxxxx/
>   https://lore.kernel.org/202605021450.ca5QGqLH-lkp@xxxxxxxxx/

Gmail labelled them as spam :-(

I think this should be fixed as below, but Steve needs to look it over.

David
---
commit dd962b95985a8b5bc564c5c4f6c48edbc2cbc02d
Author: David Howells <dhowells@xxxxxxxxxx>
Date:   Mon May 18 21:45:45 2026 +0100

    cifs: Fix undefined variables
    
    Fix a couple of undefined variables introduced by the patch to fix tearing
    on ->remote_i_size and ->zero_point.  For some reason, make W=1 with gcc
    doesn't give undefined variable warnings (but clang does).
    
    Fixes: 2c8f4742bb76 ("netfs: Fix potential for tearing in ->remote_i_size and ->zero_point")
    Reported-by: kernel test robot <lkp@xxxxxxxxx>
    Closes: https://lore.kernel.org/oe-kbuild-all/202605031459.eX5UbO3K-lkp@xxxxxxxxx/
    Closes: https://lore.kernel.org/oe-kbuild-all/202605021450.ca5QGqLH-lkp@xxxxxxxxx/
    cc: Steve French <sfrench@xxxxxxxxx>
    cc: Paulo Alcantara <pc@xxxxxxxxxxxxx>
    cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
    cc: Christian Brauner <brauner@xxxxxxxxxx>
    cc: linux-cifs@xxxxxxxxxxxxxxx
    cc: netfs@xxxxxxxxxxxxxxx
    cc: linux-fsdevel@xxxxxxxxxxxxxxx

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index feac491c5070..f557eb7875c7 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -1304,7 +1304,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	struct cifsFileInfo *smb_file_src = src_file->private_data;
 	struct cifsFileInfo *smb_file_target = dst_file->private_data;
 	struct cifs_tcon *target_tcon, *src_tcon;
-	unsigned long long i_size, old_size, new_size, zero_point;
+	unsigned long long i_size, new_size;
 	unsigned long long destend, fstart, fend;
 	unsigned int xid;
 	int rc;
@@ -1372,7 +1372,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 		goto unlock;
 
 	spin_lock(&target_inode->i_lock);
-	if (fend > zero_point)
+	if (fend > target_cifsi->netfs._zero_point)
 		netfs_write_zero_point(target_inode, fend + 1);
 	i_size = target_inode->i_size;
 	spin_unlock(&target_inode->i_lock);
@@ -1387,7 +1387,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	if (target_tcon->ses->server->ops->duplicate_extents) {
 		rc = target_tcon->ses->server->ops->duplicate_extents(xid,
 			smb_file_src, smb_file_target, off, len, destoff);
-		if (rc == 0 && new_size > old_size) {
+		if (rc == 0 && new_size > i_size) {
 			truncate_setsize(target_inode, new_size);
 			fscache_resize_cookie(cifs_inode_cookie(target_inode),
 					      new_size);