Hi David, I'm observing a hang with the recent 3.4-ish kernel when trying to do something like the below: mount -t nfs4 server:/share /mnt/nfs -o fsc cp /mnt/nfs/f_20M /tmp echo 3 > /proc/sys/vm/drop_caches cp /mnt/nfs/f_20M /share The second cp hangs. Apparently, the cp process seems to be waiting to get exclusive access to a page that is already been locked but not released.. Here's a snip from SysRq + w output [1898655.285852] SysRq : Show Blocked State [1898655.285864] task PC stack pid father [1898655.285909] cp D 0000000000000000 0 20090 20083 0x00000000 [1898655.285913] ffff8804252b7bd8 0000000000000086 ffff880424334df0 ffff8804252b6010 [1898655.285917] 0000000000011180 0000000000011180 ffff8804252b7fd8 ffff8804252b7fd8 [1898655.285920] 0000000000011180 ffff8804248aa280 000000011c498cd4 ffffffff81a0b020 [1898655.285924] Call Trace: [1898655.285939] [<ffffffff81441bbc>] io_schedule+0x9c/0xf0 [1898655.285946] [<ffffffff810ef999>] sleep_on_page_killable+0x9/0x40 [1898655.285950] [<ffffffff810efa66>] __lock_page_killable+0x96/0xd0 [1898655.285954] [<ffffffff810f0c57>] do_generic_file_read+0x227/0x490 [1898655.285959] [<ffffffff810f151c>] generic_file_aio_read+0xfc/0x260 [1898655.285977] [<ffffffffa04a4cf1>] nfs_file_read+0xf1/0x140 [nfs] [1898655.285996] [<ffffffff8114fea0>] do_sync_read+0xc0/0x100 [1898655.286000] [<ffffffff81150647>] vfs_read+0xc7/0x130 [1898655.286004] [<ffffffff811507b3>] sys_read+0x53/0xa0 [1898655.286009] [<ffffffff8144b692>] system_call_fastpath+0x16/0x1b [1898655.286026] [<00007f243130b1a0>] 0x7f243130b19f It's likely that the process that had acquired a lock on the page has already excited. I see a similar report in the cache-fs mailing list https://www.redhat.com/archives/linux-cachefs/2012-August/msg00000.html I haven't enabled fscache and cachefiles debugging, yet. Before doing so, I thought I'll just check whether you see the problem and if it sounds familiar to you. Thanks Suresh -- Linux-cachefs mailing list Linux-cachefs@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cachefs