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Documentation: fix wrong value in md.txt

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In the current Documentation/md.txt, the lower limit value of
stripe_cache_size is 16 and the default value is 128, but when
I update kernel to the latest mainline version and RAID5 array
is created by mdadm, then execute the following commands, it
shows an error and a difference respectively.

1) set stripe_cache_size to 16
[root@localhost ~]# echo 16 > /sys/block/md0/md/stripe_cache_size
bash: echo: write error: Invalid argument
2) read the default value of stripe_cache_size
[root@localhost ~]# cat /sys/block/md0/md/stripe_cache_size
256

I read drivers/md/raid5.c and find the following related code:
1) in function 'raid5_set_cache_size':
if (size <= 16 || size > 32768)
	return -EINVAL;
2) #define NR_STRIPES		256

So the lower limit value of stripe_cache_size should be 17 and
the default value should be 256.

Signed-off-by: Tiezhu Yang <kernelpatch@126.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Tiezhu Yang 2016-06-17 09:40:02 +08:00 committed by Jonathan Corbet
parent c0b8c9a344
commit a37376f326
1 changed files with 1 additions and 1 deletions
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Documentation/md.txt
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@ -602,7 +602,7 @@ These currently include
stripe_cache_size (currently raid5 only)
number of entries in the stripe cache. This is writable, but
there are upper and lower limits (32768, 16). Default is 128.
there are upper and lower limits (32768, 17). Default is 256.
strip_cache_active (currently raid5 only)
number of active entries in the stripe cache
preread_bypass_threshold (currently raid5 only)