On Tue, Dec 18, 2018 at 04:02:21PM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From d57f9da890696af1484f4a47f7f123560197865a Mon Sep 17 00:00:00 2001
From: Damien Le Moal <damien.lemoal@xxxxxxx>
Date: Fri, 30 Nov 2018 15:31:48 +0900
Subject: [PATCH] dm zoned: Fix target BIO completion handling
struct bioctx includes the ref refcount_t to track the number of I/O
fragments used to process a target BIO as well as ensure that the zone
of the BIO is kept in the active state throughout the lifetime of the
BIO. However, since decrementing of this reference count is done in the
target .end_io method, the function bio_endio() must be called multiple
times for read and write target BIOs, which causes problems with the
value of the __bi_remaining struct bio field for chained BIOs (e.g. the
clone BIO passed by dm core is large and splits into fragments by the
block layer), resulting in incorrect values and inconsistencies with the
BIO_CHAIN flag setting. This is turn triggers the BUG_ON() call:
BUG_ON(atomic_read(&bio->__bi_remaining) <= 0);
in bio_remaining_done() called from bio_endio().
Fix this ensuring that bio_endio() is called only once for any target
BIO by always using internal clone BIOs for processing any read or
write target BIO. This allows reference counting using the target BIO
context counter to trigger the target BIO completion bio_endio() call
once all data, metadata and other zone work triggered by the BIO
complete.
Overall, this simplifies the code too as the target .end_io becomes
unnecessary and differences between read and write BIO issuing and
completion processing disappear.
Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
This patch depends on 092b5648760a ("dm zoned: target: use refcount_t
for dm zoned reference counters"), it might make sense to just take it
as is instead of backporting d57f9da89069.
--
Thanks,
Sasha
