Messages in this thread | | | Date | Tue, 08 Dec 2009 18:13:32 +0800 | From | Cong Wang <> | Subject | Re: [Patch] fs: remove a useless BUG() |
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Andrew Morton wrote: > On Mon, 30 Nov 2009 21:34:14 -0500 > Amerigo Wang <amwang@redhat.com> wrote: > >> This BUG() is suspicious, it makes its following statements >> unreachable, and it seems to be useless, since the caller >> of this function already handles the failure properly. >> Remove it. >> >> Signed-off-by: WANG Cong <amwang@redhat.com> >> Cc: Alexander Viro <viro@zeniv.linux.org.uk> >> Cc: Jens Axboe <jens.axboe@oracle.com> >> Cc: Nick Piggin <npiggin@suse.de> >> Cc: "Theodore Ts'o" <tytso@mit.edu> >> >> --- >> diff --git a/fs/buffer.c b/fs/buffer.c >> index 6fa5302..ac111d7 100644 >> --- a/fs/buffer.c >> +++ b/fs/buffer.c >> @@ -1041,7 +1041,6 @@ grow_dev_page(struct block_device *bdev, sector_t block, >> return page; >> >> failed: >> - BUG(); >> unlock_page(page); >> page_cache_release(page); >> return NULL; > > The caller doesn't handle this properly. If we return zero here, > grow_buffers() will say sheesh and will retry and the kernel goes into > an infinite retry loop. > > If there is a blockdev page which is sitting in pagecache and for some > reason it has buffers and we cannot release them, we're kind of stuck > and don't know what to do. Going BUG() is a decent thing to do here. > > I don't think I've ever seen a report of the BUG triggering. It could > happen as a result of memory corruption or a missed bh_put() or > whatever. >
Oh, good explanation!
> I think a better patch would be to remove the > unlock_page()/page_cache_release(), add a comment (culled from the > above) and leave the BUG() there. >
Ok, I will prepare a patch tomorrow.
Thanks!
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