From 5dbd571d875d73e087c1eeb3d840cfc653a97422 Mon Sep 17 00:00:00 2001 From: "Alexander V. Lukyanov" Date: Mon, 21 Feb 2011 21:33:21 -0500 Subject: [PATCH] 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 Signed-off-by: "Theodore Ts'o" --- fs/ext4/super.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ext4/super.c b/fs/ext4/super.c index ef83457fd4ea..a1ac24b6a758 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -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; -- 2.20.1