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For some nvme command, when issued by the nvme core layer, there is an internal buffer which can cause blk_rq_payload_bytes() to return a non-zero value yet there is no actual/real command payload and sg list. An example is the WRITE ZEROES command. To address this, when making choices on whether to dma map an sgl, use blk_rq_nr_phys_segments() instead of blk_rq_payload_bytes(). When there is a sgl, blk_rq_payload_bytes() will return the amount of data to be transferred by the sgl. Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Signed-off-by: James Smart <jsmart2021@gmail.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.