On Mon, Nov 7, 2011 at 15:10, Sage Weil <sage@xxxxxxxxxxxx> wrote: > It applies to RBD too... _if_ the ceph-osd process is calling sync(2). > On btrfs it doesn't, and on XFS/extN/etc., it only does on older kernels > with older glibc. New kernels (.39+) and new glibc have syncfs(2), which > syncs only the fs the ceph-osd is serving up. > > http://linux.die.net/man/2/syncfs I'm willing to believe syncfs(2) makes the deadlock more rare, but isn't it still possible? e.g. see slide 23 of www.scs.stanford.edu/nyu/02fa/notes/l3.pdf for a description of this in context of loopback NFS. If rbd.ko does write caching, and uses buffer cache for it: 1. ceph-osd reads a file from local disk 2. the fs needs to allocate a buffer 3. vm chooses dirty buffer in rbd cache to flush 4. rbd.ko blocks waiting for ceph-osd, which is waiting to read the file from disk in step 1. -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
