Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.
Martin K. Petersen
authored
Now that zeroout and discards are distinct operations we need to separate the policy of choosing the appropriate command. Create a zeroing_mode which can be one of: write: Zeroout assist not present, use regular WRITE writesame: Allow WRITE SAME(10/16) with a zeroed payload writesame_16_unmap: Allow WRITE SAME(16) with UNMAP writesame_10_unmap: Allow WRITE SAME(10) with UNMAP The last two are conditional on the device being thin provisioned with LBPRZ=1 and LBPWS=1 or LBPWS10=1 respectively. Whether to set the UNMAP bit or not depends on the REQ_NOUNMAP flag. And if none of the _unmap variants are supported, regular WRITE SAME will be used if the device supports it. The zeroout_mode is exported in sysfs and the detected mode for a given device can be overridden using the string constants above. With this change in place we can now issue WRITE SAME(16) with UNMAP set for block zeroing applications that require hard guarantees and logical_block_size granularity. And at the same time use the UNMAP command with the device's preferred granulary and alignment for discard operations. Signed-off-by:Martin K. Petersen <martin.petersen@oracle.com> Signed-off-by:
Christoph Hellwig <hch@lst.de> Reviewed-by:
Hannes Reinecke <hare@suse.com> Signed-off-by:
Jens Axboe <axboe@fb.com>