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Allow block drivers to configure the following: * Maximum number of hardware sectors values smaller than PAGE_SIZE >> SECTOR_SHIFT. For PAGE_SIZE = 4096 this means that values below 8 become supported. * A maximum segment size below the page size. This is most useful for page sizes above 4096 bytes. The blk_sub_page_segments static branch will be used in later patches to prevent that performance of block drivers that support segments >= PAGE_SIZE and max_hw_sectors >= PAGE_SIZE >> SECTOR_SHIFT would be affected. This patch may change the behavior of existing block drivers from not working into working. If a block driver calls blk_queue_max_hw_sectors() or blk_queue_max_segment_size(), this is usually done to configure the maximum supported limits. An attempt to configure a limit below what is supported by the block layer causes the block layer to select a larger value. If that value is not supported by the block driver, this may cause other data to be transferred than requested, a kernel crash or other undesirable behavior. Keeps the ABI stable by taking advantage of a hole in the structure! Bug: 308663717 Bug: 319125789 Bug: 324152549 Change-Id: I4a7b605f0f0d82dde0b4703496c7314064f48acb Signed-off-by: Bart Van Assche <bvanassche@acm.org> [jyescas@google.com: disable subpage limits in block/blk-sysfs.c instead block/blk-core.c because the function blk_free_queue() is not defined in 5.15 kernel] Signed-off-by: Juan Yescas <jyescas@google.com>