ext4: prevent parallel resizers by atomic bit ops
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>
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 808c554..f18bfe3 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -202,8 +202,9 @@
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 @@
if (err == 0)
err = err2;
mnt_drop_write(filp->f_path.mnt);
+ ext4_resize_end(sb);
return err;
}
@@ -271,8 +273,9 @@
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 @@
if (err == 0)
err = err2;
mnt_drop_write(filp->f_path.mnt);
+ ext4_resize_end(sb);
return err;
}