b571cfcb9d
When NFS requests are split into sub-requests, nfs_inode_remove_request calls nfs_page_group_sync_on_bit to set PG_REMOVE on this sub-request and only completes the head requests once PG_REMOVE is set on all requests. This means that when nfs_lock_and_join_requests sees a PG_REMOVE bit, I/O on the request is in progress and has partially completed. If such a request is returned to nfs_try_to_update_request, it could be extended with the newly dirtied region and I/O for the combined range will be re-scheduled, leading to extra I/O. Change the logic to instead restart the search for a request when any PG_REMOVE bit is set, as the completion handler will remove the request as soon as it can take the page group lock. This not only avoid extending the I/O but also does the right thing for the callers that want to cancel or flush the request. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.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 reStructuredText 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.