Hi, Milosz I am not very sure about how to enable caching in write path. I just compile the latest kernel with "Enable Ceph client caching support", start cachefilesd, and mount cephfs with -o fsc. Then, the kernel will panic easily when the script runs to "dd if=cephfs/foo of=/dev/null bs=8 count=1024" 2013/12/27 Milosz Tanski <milosz@xxxxxxxxx>: > Li, > > I looked at the patchset am I correct that this only happens when we > enable caching in the write path? > > - Milosz > > On Thu, Dec 26, 2013 at 9:29 AM, Li Wang <liwang@xxxxxxxxxxxxxxx> wrote: >> From: Yunchuan Wen <yunchuanwen@xxxxxxxxxxxxxxx> >> >> The following scripts could easily panic the kernel, >> >> #!/bin/bash >> mount -t ceph -o fsc MONADDR:/ cephfs >> rm -rf cephfs/foo >> dd if=/dev/zero of=cephfs/foo bs=8 count=512 >> echo 3 > /proc/sys/vm/drop_caches >> dd if=cephfs/foo of=/dev/null bs=8 count=1024 >> >> This is due to when writing a page into fscache, the code will >> assert that the write position does not exceed the >> object->store_limit_l, which is supposed to be equal to inode->i_size. >> However, for current implementation, after file writing, the >> object->store_limit_l is not synchronized with new >> inode->i_size immediately, which introduces a race that if writing >> a new page into fscache, will reach the ASSERT that write position >> has exceeded the object->store_limit_l, and cause kernel panic. >> This patch fixes it. >> >> Yunchuan Wen (3): >> Ceph fscache: Add an interface to synchronize object store limit >> Ceph fscache: Update object store limit after writing >> Ceph fscache: Wait for completion of object initialization >> >> fs/ceph/cache.c | 1 + >> fs/ceph/cache.h | 10 ++++++++++ >> fs/ceph/file.c | 3 +++ >> 3 files changed, 14 insertions(+) >> >> -- >> 1.7.9.5 >> > > > > -- > Milosz Tanski > CTO > 10 East 53rd Street, 37th floor > New York, NY 10022 > > p: 646-253-9055 > e: milosz@xxxxxxxxx > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
