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ext4: prevent parallel resizers by atomic bit ops

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Before this patch, parallel resizers are allowed and protected by a
mutex lock, actually, there is no need to support parallel resizer, so
this patch prevents parallel resizers by atmoic bit ops, like
lock_page() and unlock_page() do.

To do this, the patch removed the mutex lock s_resize_lock from struct
ext4_sb_info and added a unsigned long field named s_resize_flags
which inidicates if there is a resizer.

Signed-off-by: Yongqiang Yang <xiaoqiangnk@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Yongqiang Yang
2011-07-26 21:35:44 -04:00
committed by Theodore Ts'o
parent 2d859db3e4
commit 8f82f840ec
4 changed files with 36 additions and 40 deletions
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12
fs/ext4/ioctl.c
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@@ -202,8 +202,9 @@ setversion_out:
struct super_block *sb = inode->i_sb;
int err, err2=0;
if (!capable(CAP_SYS_RESOURCE))
return -EPERM;
err = ext4_resize_begin(sb);
if (err)
return err;
if (get_user(n_blocks_count, (__u32 __user *)arg))
return -EFAULT;
@@ -221,6 +222,7 @@ setversion_out:
if (err == 0)
err = err2;
mnt_drop_write(filp->f_path.mnt);
ext4_resize_end(sb);
return err;
}
@@ -271,8 +273,9 @@ mext_out:
struct super_block *sb = inode->i_sb;
int err, err2=0;
if (!capable(CAP_SYS_RESOURCE))
return -EPERM;
err = ext4_resize_begin(sb);
if (err)
return err;
if (copy_from_user(&input, (struct ext4_new_group_input __user *)arg,
sizeof(input)))
@@ -291,6 +294,7 @@ mext_out:
if (err == 0)
err = err2;
mnt_drop_write(filp->f_path.mnt);
ext4_resize_end(sb);
return err;
}