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[ Upstream commit2e586641c9] We will only track the uppest parent snapshot realm from which we need to rebuild the snapshot contexts _downward_ in hierarchy. For all the others having no new snapshot we will do nothing. This fix will avoid calling ceph_queue_cap_snap() on some inodes inappropriately. For example, with the code in mainline, suppose there are 2 directory hierarchies (with 6 directories total), like this: /dir_X1/dir_X2/dir_X3/ /dir_Y1/dir_Y2/dir_Y3/ Firstly, make a snapshot under /dir_X1/dir_X2/.snap/snap_X2, then make a root snapshot under /.snap/root_snap. Every time we make snapshots under /dir_Y1/..., the kclient will always try to rebuild the snap context for snap_X2 realm and finally will always try to queue cap snaps for dir_Y2 and dir_Y3, which makes no sense. That's because the snap_X2's seq is 2 and root_snap's seq is 3. So when creating a new snapshot under /dir_Y1/... the new seq will be 4, and the mds will send the kclient a snapshot backtrace in _downward_ order: seqs 4, 3. When ceph_update_snap_trace() is called, it will always rebuild the from the last realm, that's the root_snap. So later when rebuilding the snap context, the current logic will always cause it to rebuild the snap_X2 realm and then try to queue cap snaps for all the inodes related in that realm, even though it's not necessary. This is accompanied by a lot of these sorts of dout messages: "ceph: queue_cap_snap 00000000a42b796b nothing dirty|writing" Fix the logic to avoid this situation. Also, the 'invalidate' word is not precise here. In actuality, it will cause a rebuild of the existing snapshot contexts or just build non-existent ones. Rename it to 'rebuild_snapcs'. URL: https://tracker.ceph.com/issues/44100 Signed-off-by: Xiubo Li <xiubli@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> Stable-dep-of:51884d153f("ceph: avoid putting the realm twice when decoding snaps fails") Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.