Commit 5dbd571d authored Feb 21, 2011 by Alexander V. Lukyanov Committed by Theodore Ts'o Feb 21, 2011

ext4: allow inode_readahead_blks=0 (linux-2.6.37)



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>

parent 7dc57615

fs/ext4/super.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1771,7 +1771,7 @@ set_qf_format:
		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;

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