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ext4: allow inode_readahead_blks=0 (linux-2.6.37)

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I cannot disable inode-read-ahead feature of ext4 (on 2.6.37):

# echo 0 > /sys/fs/ext4/sda2/inode_readahead_blks 
bash: echo: write error: Invalid argument

On a server with lots of small files and random access this read-ahead makes
performance worse, and I'd like to disable it. I work around this problem
by using value of 1, but it still reads an extra block.

This patch fixes the problem by checking for zero explicitly.

Signed-off-by: Alexander V. Lukyanov <lav@netis.ru>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Alexander V. Lukyanov 2011-02-21 21:33:21 -05:00 committed by Theodore Ts'o
parent 7dc576158d
commit 5dbd571d87
1 changed files with 2 additions and 2 deletions
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4
fs/ext4/super.c
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@ -1771,7 +1771,7 @@ static int parse_options(char *options, struct super_block *sb,
return 0;
if (option < 0 || option > (1 << 30))
return 0;
if (!is_power_of_2(option)) {
if (option && !is_power_of_2(option)) {
ext4_msg(sb, KERN_ERR,
"EXT4-fs: inode_readahead_blks"
" must be a power of 2");
@ -2412,7 +2412,7 @@ static ssize_t inode_readahead_blks_store(struct ext4_attr *a,
if (parse_strtoul(buf, 0x40000000, &t))
return -EINVAL;
if (!is_power_of_2(t))
if (t && !is_power_of_2(t))
return -EINVAL;
sbi->s_inode_readahead_blks = t;