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vfs: bogus warnings in fs/namei.c

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The follow_link() function always initializes its *p argument,
or returns an error, but when building with 'gcc -s', the compiler
gets confused by the __always_inline attribute to the function
and can no longer detect where the cookie was initialized.

The solution is to always initialize the pointer from follow_link,
even in the error path. When building with -O2, this has zero impact
on generated code and adds a single instruction in the error path
for a -Os build on ARM.

Without this patch, building with gcc-4.6 through gcc-4.8 and
CONFIG_CC_OPTIMIZE_FOR_SIZE results in:

fs/namei.c: In function 'link_path_walk':
fs/namei.c:649:24: warning: 'cookie' may be used uninitialized in this function [-Wuninitialized]
fs/namei.c:1544:9: note: 'cookie' was declared here
fs/namei.c: In function 'path_lookupat':
fs/namei.c:649:24: warning: 'cookie' may be used uninitialized in this function [-Wuninitialized]
fs/namei.c:1934:10: note: 'cookie' was declared here
fs/namei.c: In function 'path_openat':
fs/namei.c:649:24: warning: 'cookie' may be used uninitialized in this function [-Wuninitialized]
fs/namei.c:2899:9: note: 'cookie' was declared here

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Arnd Bergmann 2012-10-11 13:20:00 +00:00 committed by Al Viro
parent 808d4e3cfd
commit 98f6ef64b1
1 changed files with 1 additions and 0 deletions
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fs/namei.c
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@ -810,6 +810,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p)
return error;
out_put_nd_path:
*p = NULL;
path_put(&nd->path);
path_put(link);
return error;