On Wed, 11 Apr 2012 17:51:57 -0300 Glauber Costa <glommer@xxxxxxxxxxxxx> wrote: > On 04/11/2012 05:26 PM, Andrew Morton wrote: > >> > >> > failed: > >> > - BUG(); > >> > unlock_page(page); > >> > page_cache_release(page); > >> > return NULL; > > Cute. > > > > AFAICT what happened was that in my April 2002 rewrite of this code I > > put a non-fatal buffer_error() warning in that case to tell us that > > something bad happened. > > > > Years later we removed the temporary buffer_error() and mistakenly > > replaced that warning with a BUG(). Only it*can* happen. > > > > We can remove the BUG() and fix up callers, or we can pass retry=1 into > > alloc_page_buffers(), so grow_dev_page() "cannot fail". Immortal > > functions are a silly fiction, so we should remove the BUG() and fix up > > callers. > > > Any particular caller you are concerned with ? Didn't someone see a buggy caller in btrfs? I'm thinking that we should retain some sort of assertion (a WARN_ON) if the try_to_free_buffers() failed. This is a weird case which I assume handles the situation where a blockdev's blocksize has changed. The code tries to throw away the old wrongly-sized buffer_heads and to then add new correctly-sized ones. If that discarding of buffers fails then the kernel is in rather a mess. It's quite possible that this code is never executed - we _should_ have invalidated all the pagecache for that device when changing blocksize. Or maybe it *is* executed, I dunno. It's one of those things which has hung around for decades as code in other places has vastly changed. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>