> Andrew Morton wrote: > > On Sun, 18 Feb 2007 19:28:18 +0100 Miklos Szeredi <[EMAIL PROTECTED]> wrote: > > > >> I was testing the new fuse shared writable mmap support, and finding > >> that bash-shared-mapping deadlocks (which isn't so strange ;). What > >> is more strange is that this is not an OOM situation at all, with > >> plenty of free and cached pages. > >> > >> A little more investigation shows that a similar deadlock happens > >> reliably with bash-shared-mapping on a loopback mount, even if only > >> half the total memory is used. > >> > >> The cause is slightly different in the two cases: > >> > >> - loopback mount: allocation by the underlying filesystem is stalled > >> on throttle_vm_writeout() > >> > >> - fuse-loop: page dirtying on the underlying filesystem is stalled on > >> balance_dirty_pages() > >> > >> In both cases the underlying fs is totally innocent, with no > >> dirty/writback pages, yet it's waiting for the global dirty+writeback > >> to go below the threshold, which obviously won't, until the > >> allocation/dirtying succeeds. > >> > >> I'm not quite sure what the solution is, and asking for thoughts. > > > > But.... these things don't just throttle. They also perform large amounts > > of writeback, which causes the dirty levels to subside. > > > >>From your description it appears that this writeback isn't happening, or > > isn't working. How come? > > Is the fuse daemon trying to do writeback to itself, perhaps? > > That is, trying to write out data to the FUSE filesystem, for which > it is also the server.
No. It's trying to write out data to a different filesystem. Trying to write out data to itself very obviously deadlocks, but that doesn't affect anything beside the stupid filesystem itself, and there are mechanisms for aborting such a situation (forced umount, abort through fuse-control filesystem). Miklos - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/