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COMPARE AND WRITE command execution starts with a call of sbc_compare_and_write(). That function locks the caw_sem member in the backend device data structure and submits a read request to the backend driver. Upon successful completion of the read compare_and_write_callback() gets called. That last function compares the data that has been read. If it matches transport_complete_callback is set to compare_and_write_post and a write request is submitted. compare_and_write_post() submits a write request to the backend driver. XDWRITEREAD command execution starts with sbc_execute_rw() submitting a read to the backend device. Upon successful completion of the read the xdreadwrite_callback() gets called. That function xors the data that has been read with the data in the data-out buffer and stores the result in the data-in buffer. Call transport_complete_callback() not only if COMPARE AND WRITE fails but also if XDWRITEREAD fails. This makes the code more systematic. Make sure that the callback functions handle (cmd, false, NULL) argument triples fine. Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org> Cc: Mike Christie <mchristi@redhat.com> Cc: Hannes Reinecke <hare@suse.de> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.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.
See Documentation/00-INDEX for a list of what is contained in each file.
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.