Re: [PATCH v2] btrfs-progs: fix discard support check

On Sun, Nov 14, 2021 at 06:43:20AM +0800, Wang Yugui wrote:

[BUG]
mkfs.btrfs(v5.15) output a message even if the disk is a HDD without
TRIM/DISCARD support.
  Performing full device TRIM /dev/sdc2 (326.03GiB) ...

[CAUSE]
mkfs.btrfs check TRIM/DISCARD support through the content of
queue/discard_granularity, but compare it against a wrong value.

When HDD without TRIM/DISCARD support, the content of
queue/discard_granularity is '0' '\n' '\0', rather than '0' '\0'.

[FIX]
- compare the value based on atoi() to provide more robustness
- delete unnecessary '\n' in pr_verbose()

Fixes: c50c448518bb ("btrfs-progs: do sysfs detection of device discard capability")
Signed-off-by: Wang Yugui <redacted>

Added to devel, thanks.