On Wed, Feb 10, 2016 at 08:13:09PM -0700, Jeff Merkey wrote:
> Here are the sources of several bugs I have seen recently in ext4 I am
> pretty sure with a null bh. One good check is to set the BUG() macro
> NOT TO call unreachable() as a build test since the compiler will
> ignore uninitialized variables in a function if someone calls BUG()
> even conditionally, and never report them during build.
>
> The following are from v4.4.1 with a BUG() macro with the call to
> unreachable() removed:
I checked all of the fs/ext4 warnings you listed and they are all
false positives.
> In file included from fs/ext4/file.c:30:0:
> fs/ext4/ext4_jbd2.h: In function ‘ext4_inode_journal_mode’:
> fs/ext4/ext4_jbd2.h:409:1: warning: control reaches end of non-void
> function [-Wreturn-type]
> }
This is from a:
if (foo) {
...
return foobie;
} else if (bar) {
...
return barbie;
} else {
BUG();
}
construct.
> fs/ext4/inode.c: In function ‘ext4_map_blocks’:
> fs/ext4/inode.c:548:5: warning: ‘retval’ may be used uninitialized in
> this function [-Wmaybe-uninitialized]
> if (retval > 0 && map->m_flags & EXT4_MAP_MAPPED) {
> ^
> fs/ext4/extents.c:2305:14: warning: ‘len’ may be used uninitialized in
> this function [-Wmaybe-uninitialized]
> ext4_lblk_t len;
> ^
All of the may be used uninitialized warnings are from a:
if (foo) {
...
retval = xxx;
} else if (bar) {
...
retval = yyy;
} else {
BUG();
}
construct.
It may be that there are some false warnings, but they certainly weren't
from warnings you've listed from ext4.
Cheers,
- Ted
