| Message ID | fb54084d-6d4e-4cda-8941-addc8c8898f5@paulmck-laptop (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC,netfs] Fix uninitialized variable in netfs_retry_read_subrequests() | expand |
Paul E. McKenney <paulmck@kernel.org> wrote: > This should actually be considered more of a bug report than a patch. > > Clang 18.1.8 (but not GCC 11.5.0) complains that the "subreq" local > variable can be used uninitialized in netfs_retry_read_subrequests(), > just after the abandon_after label. This function is unusual in having > three instances of this local variable. The third and last one is clearly > erroneous because there is a branch out of the enclosing do-while loop > to the end of this function, and it looks like the intent is that the > code at the end of this function be using the same value of the "subreq" > local variable as is used within that do-while loop. > > Therefore, take the obvious (if potentially quite misguided) approach > of removing the third declaration of "subreq", instead simply setting > it to NULL. I think you're looking at the old version of my netfs-writeback branch that's residing in Christian's vfs.netfs branch. I've posted a new version of my branch[1] without this problem and am hoping for Christian to update the branch[2] so that Stephen can pull it into linux-next. David [1] https://lore.kernel.org/linux-fsdevel/20241216204124.3752367-1-dhowells@redhat.com/T/#t [2] And hoping he'll remember to drop "[PATCH v5 26/32] Display waited-on page index after 1min of waiting" for me. I forgot to remove that debugging patch.
On Fri, Dec 20, 2024 at 12:20:11AM +0000, David Howells wrote: > Paul E. McKenney <paulmck@kernel.org> wrote: > > > This should actually be considered more of a bug report than a patch. > > > > Clang 18.1.8 (but not GCC 11.5.0) complains that the "subreq" local > > variable can be used uninitialized in netfs_retry_read_subrequests(), > > just after the abandon_after label. This function is unusual in having > > three instances of this local variable. The third and last one is clearly > > erroneous because there is a branch out of the enclosing do-while loop > > to the end of this function, and it looks like the intent is that the > > code at the end of this function be using the same value of the "subreq" > > local variable as is used within that do-while loop. > > > > Therefore, take the obvious (if potentially quite misguided) approach > > of removing the third declaration of "subreq", instead simply setting > > it to NULL. > > I think you're looking at the old version of my netfs-writeback branch that's > residing in Christian's vfs.netfs branch. I've posted a new version of my > branch[1] without this problem and am hoping for Christian to update the > branch[2] so that Stephen can pull it into linux-next. Me too, and thank you for looking into this! Thanx, Paul > David > > [1] https://lore.kernel.org/linux-fsdevel/20241216204124.3752367-1-dhowells@redhat.com/T/#t > > [2] And hoping he'll remember to drop "[PATCH v5 26/32] Display waited-on page > index after 1min of waiting" for me. I forgot to remove that debugging patch. >
diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c index 8ca0558570c14..eba684b408df1 100644 --- a/fs/netfs/read_retry.c +++ b/fs/netfs/read_retry.c @@ -72,12 +72,14 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq) next = stream->subrequests.next; do { - struct netfs_io_subrequest *subreq = NULL, *from, *to, *tmp; + struct netfs_io_subrequest *from, *to, *tmp; struct iov_iter source; unsigned long long start, len; size_t part; bool boundary = false; + subreq = NULL; + /* Go through the subreqs and find the next span of contiguous * buffer that we then rejig (cifs, for example, needs the * rsize renegotiating) and reissue.