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2ccb45462a
The MDS is getting a new lock-caching facility that will allow it to cache the necessary locks to allow asynchronous directory operations. Since the CEPH_CAP_FILE_* caps are currently unused on directories, we can repurpose those bits for this purpose. When performing an unlink, if we have Fx on the parent directory, and CEPH_CAP_DIR_UNLINK (aka Fr), and we know that the dentry being removed is the primary link, then then we can fire off an unlink request immediately and don't need to wait on reply before returning. In that situation, just fix up the dcache and link count and return immediately after issuing the call to the MDS. This does mean that we need to hold an extra reference to the inode being unlinked, and extra references to the caps to avoid races. Those references are put and error handling is done in the r_callback routine. If the operation ends up failing, then set a writeback error on the directory inode, and the inode itself that can be fetched later by an fsync on the dir. The behavior of dir caps is slightly different from caps on normal files. Because these are just considered an optimization, if the session is reconnected, we will not automatically reclaim them. They are instead considered lost until we do another synchronous op in the parent directory. Async dirops are enabled via the "nowsync" mount option, which is patterned after the xfs "wsync" mount option. For now, the default is "wsync", but eventually we may flip that. Signed-off-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: "Yan, Zheng" <zyan@redhat.com> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
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.