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When a read is directed to the cache, we risk that the lba has been updated during the time we made the L2P table lookup and the time we are actually reading form the cache. We intentionally not hold the L2P lock not to block other threads. While strict ordering is not a guarantee at this level (unless REQ_FLUSH has been previously issued), we have experience that some databases that have recently implemented direct I/O support, issue metadata reads very close to the writes, without issuing a fsync in the middle. An easy way to support them while they is to make an extra effort and check the L2P map right before reading the cache. Signed-off-by: Javier González <javier@cnexlabs.com> Signed-off-by: Matias Bjørling <matias@cnexlabs.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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.