mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-01 08:46:36 +09:00
e477b24b50
When gfs2 does metadata I/O, only REQ_META is used as a metadata hint of the bio. But flag REQ_META is just a hint for block trace, not for block layer code to handle a bio as metadata request. For some of metadata I/Os of gfs2, A REQ_PRIO flag on the metadata bio would be very informative to block layer code. For example, if bcache is used as a I/O cache for gfs2, it will be possible for bcache code to get the hint and cache the pre-fetched metadata blocks on cache device. This behavior may be helpful to improve metadata I/O performance if the following requests hit the cache. Here are the locations in gfs2 code where a REQ_PRIO flag should be added, - All places where REQ_READAHEAD is used, gfs2 code uses this flag for metadata read ahead. - In gfs2_meta_rq() where the first metadata block is read in. - In gfs2_write_buf_to_page(), read in quota metadata blocks to have them up to date. These metadata blocks are probably to be accessed again in future, adding a REQ_PRIO flag may have bcache to keep such metadata in fast cache device. For system without a cache layer, REQ_PRIO can still provide hint to block layer to handle metadata requests more properly. Signed-off-by: Coly Li <colyli@suse.de> Signed-off-by: Bob Peterson <rpeterso@redhat.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.