On Wed, Jul 29, 2015 at 01:54:12PM +0200, Michal Hocko wrote: > On Tue 21-07-15 10:58:59, Michal Hocko wrote: > > [CCing more people from a potentially affected fs - the reference to the > > email thread is: http://marc.info/?l=linux-mm&m=143744398020147&w=2] ... > > > The didn't used to happen, because the loop device used to issue > > > reads through the splice path and that does: > > > > > > error = add_to_page_cache_lru(page, mapping, index, > > > GFP_KERNEL & mapping_gfp_mask(mapping)); > > > > > > i.e. it pays attention to the allocation context placed on the > > > inode and so is doing GFP_NOFS allocations here and avoiding the > > > recursion problem. > > > > > > [ CC'd Michal Hocko and the mm list because it's a clear exaple of > > > why ignoring the mapping gfp mask on any page cache allocation is > > > a landmine waiting to be tripped over. ] > > > > Thank you for CCing me. I haven't noticed this one when checking for > > other similar hardcoded GFP_KERNEL users (6afdb859b710 ("mm: do not > > ignore mapping_gfp_mask in page cache allocation paths")). And there > > seem to be more of them now that I am looking closer. > > > > I am not sure what to do about fs/nfs/dir.c:nfs_symlink which doesn't > > require GFP_NOFS or mapping gfp mask for other allocations in the same > > context. > > > > What do you think about this preliminary (and untested) patch? > > Dave, did you have chance to test the patch in your environment? Is the > patch good to go or we want a larger refactoring? No, I haven't had a chance to test it yet. I'll try to get somethign done by the end of the week, but I'm not able to reliably reproduce the hang I saw (i.e. the analysis I did was from the first deadlock and I've only seen it once since) so testing is likely to be inconclusive, anyway.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
