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When a read request, which bypassed the cache, fails, we need to retry it through the cache. This involves attaching it to a sequence of stripe_heads, and it may not be possible to get all the stripe_heads we need at once. We do what we can, and record how far we got in ->bi_phys_segments so we can pick up again later. There is only ever one bio which may have a non-zero offset stored in ->bi_phys_segments, the one that is either active in the single thread which calls retry_aligned_read(), or is in conf->retry_read_aligned waiting for retry_aligned_read() to be called again. So we only need to store one offset value. This can be in a local variable passed between remove_bio_from_retry() and retry_aligned_read(), or in the r5conf structure next to the ->retry_read_aligned pointer. Storing it there allows the last usage of ->bi_phys_segments to be removed from md/raid5.c. Signed-off-by: NeilBrown <neilb@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
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.