On Tue, 08 Feb 2011, Gurudas Pai wrote: > > On Wed, 26 Jan 2011, Hugh Dickins wrote: > >> I had wanted to propose that for now you modify just fuse to use > >> i_alloc_sem for serialization there, and I provide a patch to > >> unmap_mapping_range() to give safety to whatever other cases there are > >> (I'm now sure there are other cases, but also sure that I cannot > >> safely identify them all and fix them correctly at source myself - > >> even if I found time to do the patches, they'd need at least a release > >> cycle to bed in with BUG_ONs). > > > > Since fuse is the only one where the BUG has actually been triggered, > > and since there are problems with all the proposed generic approaches, > > I concur. I didn't want to use i_alloc_sem here as it's more > > confusing than a new mutex. > > > > Gurudas, could you please give this patch a go in your testcase? > I found this BUG with nfs, so trying with current patch may not help. > https://lkml.org/lkml/2010/12/29/9 > > Let me know if I have to run this Ahh, I was not aware of that. No, in that case there's not much point in trying this patch for you as it only fixes the issue in fuse. I haven't looked at the NFS side of it yet. Added Trond to the Cc. Thanks, Miklos > > > > From: Miklos Szeredi <mszeredi@xxxxxxx> > > Subject: fuse: prevent concurrent unmap on the same inode > > > > Running a fuse filesystem with multiple open()'s in parallel can > > trigger a "kernel BUG at mm/truncate.c:475" > > > > The reason is, unmap_mapping_range() is not prepared for more than > > one concurrent invocation per inode. > > > > Truncate and hole punching already serialize with i_mutex. Other > > callers of unmap_mapping_range() do not, and it's difficult to get > > i_mutex protection for all callers. In particular ->d_revalidate(), > > which calls invalidate_inode_pages2_range() in fuse, may be called > > with or without i_mutex. > > > > This patch adds a new mutex to fuse_inode to prevent running multiple > > concurrent unmap_mapping_range() on the same mapping. > > Thanks, > -Guru > > > > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>