btrfs warning fixes for 5.15 and 5.17

Nathan Chancellor
2022-04-14T20:29:55Z

Hi Greg and Sasha,

Please apply

ad3fc7946b18 ("btrfs: remove no longer used counter when reading data page")
6d4a6b515c39 ("btrfs: remove unused variable in btrfs_{start,write}_dirty_block_groups()")

to 5.15 and 5.17 and

cd9255be6980 ("btrfs: remove unused parameter nr_pages in add_ra_bio_pages()")

to 5.15 (it landed in 5.16), as they all resolve build errors with
CONFIG_WERROR=y and tip of tree clang, which recently added support for
unary operations in -Wunused-but-set-variable. They all apply cleanly
and I do not see any additional build warnings and errors.

Commit 6d4a6b515c39 was specifically tagged for stable back to 5.4,
which should be fine, but it really only needs to go back to 5.12+, as
btrfs turned on W=1 (which includes this warning) for itself in commit
e9aa7c285d20 ("btrfs: enable W=1 checks for btrfs"), which landed in
5.12-rc1. Prior that that change, none of these warnings will be
visible under a normal build.

Cheers,
Nathan