mainline inclusion
from v5.13-rc6
commit 1616a4c2
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I59A5L?from=project-issue
CVE: N/A

------------------------------------

For read cache missing, bcache defines a readahead size for the read I/O
request to the backing device for the missing data. This readahead size
is initialized to 0, and almost no one uses it to avoid unnecessary read
amplifying onto backing device and write amplifying onto cache device.
Considering upper layer file system code has readahead logic allready
and works fine with readahead_cache_policy sysfile interface, we don't
have to keep bcache self-defined readahead anymore.

This patch removes the bcache self-defined readahead for cache missing
request for backing device, and the readahead sysfs file interfaces are
removed as well.

This is the preparation for next patch to fix potential kernel panic due
to oversized request in a simpler method.
Reported-by: NAlexander Ullrich <ealex1979@gmail.com>
Reported-by: NDiego Ercolani <diego.ercolani@gmail.com>
Reported-by: NJan Szubiak <jan.szubiak@linuxpolska.pl>
Reported-by: NMarco Rebhan <me@dblsaiko.net>
Reported-by: NMatthias Ferdinand <bcache@mfedv.net>
Reported-by: NVictor Westerhuis <victor@westerhu.is>
Reported-by: NVojtech Pavlik <vojtech@suse.cz>
Reported-and-tested-by: NRolf Fokkens <rolf@rolffokkens.nl>
Reported-and-tested-by: NThorsten Knabe <linux@thorsten-knabe.de>
Signed-off-by: NColy Li <colyli@suse.de>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Cc: stable@vger.kernel.org
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: Nix <nix@esperi.org.uk>
Cc: Takashi Iwai <tiwai@suse.com>
Link: https://lore.kernel.org/r/20210607125052.21277-2-colyli@suse.deSigned-off-by: NJens Axboe <axboe@kernel.dk>
Reviewed-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>