linux-kernel - Re: [f2fs-dev] [PATCH v4 2/2] f2fs: fix compat F2FS_IOC_{MOVE, GARBAGE_COLLECT}

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Date:   Mon, 9 Nov 2020 10:29:25 +0800
From:   Chao Yu <yuchao0@...wei.com>
To:     Eric Biggers <ebiggers@...nel.org>, Chao Yu <chao@...nel.org>
CC:     <jaegeuk@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-f2fs-devel@...ts.sourceforge.net>
Subject: Re: [f2fs-dev] [PATCH v4 2/2] f2fs: fix compat F2FS_IOC_{MOVE,
 GARBAGE_COLLECT}_RANGE

On 2020/11/8 1:16, Eric Biggers wrote:
> On Sat, Nov 07, 2020 at 05:25:23PM +0800, Chao Yu wrote:
>> On 2020/11/7 2:03, Eric Biggers wrote:
>>> On Fri, Nov 06, 2020 at 02:53:31PM +0800, Chao Yu wrote:
>>>> +#if defined(__KERNEL__)
>>>> +struct compat_f2fs_gc_range {
>>>> +	u32 sync;
>>>> +	compat_u64 start;
>>>> +	compat_u64 len;
>>>> +};
>>>
>>> There's no need to use '#if defined(__KERNEL__)' in kernel source files.
>>>
>>> Likewise for compat_f2fs_move_range.
>>
>> Correct.
>>
>>>
>>>> +static int f2fs_compat_ioc_gc_range(struct file *file, unsigned long arg)
>>>> +{
>>>> +	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(file));
>>>> +	struct compat_f2fs_gc_range __user *urange;
>>>> +	struct f2fs_gc_range range;
>>>> +	int err;
>>>> +
>>>> +	if (unlikely(f2fs_cp_error(sbi)))
>>>> +		return -EIO;
>>>> +	if (!f2fs_is_checkpoint_ready(sbi))
>>>> +		return -ENOSPC;
>>>
>>> I still don't understand why this checkpoint-related stuff is getting added
>>> here, and only to the compat versions of the ioctls.  It wasn't in the original
>>> version.  If they are needed then they should be added to __f2fs_ioc_gc_range()
>>> and __f2fs_ioc_move_range() (preferably by a separate patch) so that they are
>>
>> If so, cp-related stuff will be checked redundantly in both f2fs_ioctl() and
>> __f2fs_ioc_xxx() function for native GC_RANGE and MOVE_RANGE ioctls, it's
>> not needed.
>>
> 
> Oh I see, the cp-related checks are at the beginning of f2fs_ioctl() too.
> 
> In that case a much better approach would be to add __f2fs_ioctl() which is
> called by f2fs_ioctl() and f2fs_compat_ioctl(), and have f2fs_ioctl() and
> f2fs_compat_ioctl() do the cp-related checks but not __f2fs_ioctl().

Will this cleanup make sense to you?

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 458724c00d98..1439577108c2 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -4249,16 +4249,10 @@ struct compat_f2fs_gc_range {

  static int f2fs_compat_ioc_gc_range(struct file *file, unsigned long arg)
  {
-	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(file));
  	struct compat_f2fs_gc_range __user *urange;
  	struct f2fs_gc_range range;
  	int err;

-	if (unlikely(f2fs_cp_error(sbi)))
-		return -EIO;
-	if (!f2fs_is_checkpoint_ready(sbi))
-		return -ENOSPC;
-
  	urange = compat_ptr(arg);
  	err = get_user(range.sync, &urange->sync);
  	err |= get_user(range.start, &urange->start);
@@ -4280,16 +4274,10 @@ struct compat_f2fs_move_range {

  static int f2fs_compat_ioc_move_range(struct file *file, unsigned long arg)
  {
-	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(file));
  	struct compat_f2fs_move_range __user *urange;
  	struct f2fs_move_range range;
  	int err;

-	if (unlikely(f2fs_cp_error(sbi)))
-		return -EIO;
-	if (!f2fs_is_checkpoint_ready(sbi))
-		return -ENOSPC;
-
  	urange = compat_ptr(arg);
  	err = get_user(range.dst_fd, &urange->dst_fd);
  	err |= get_user(range.pos_in, &urange->pos_in);
@@ -4301,6 +4289,27 @@ static int f2fs_compat_ioc_move_range(struct file *file, unsigned long arg)
  	return __f2fs_ioc_move_range(file, &range);
  }

+static long __f2fs_compat_ioctl(struct file *file, unsigned int cmd,
+							unsigned long arg)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(file));
+
+	if (unlikely(f2fs_cp_error(sbi)))
+		return -EIO;
+	if (!f2fs_is_checkpoint_ready(sbi))
+		return -ENOSPC;
+
+	switch (cmd) {
+	case F2FS_IOC32_GARBAGE_COLLECT_RANGE:
+		return f2fs_compat_ioc_gc_range(file, arg);
+	case F2FS_IOC32_MOVE_RANGE:
+		return f2fs_compat_ioc_move_range(file, arg);
+	default:
+		return -ENOIOCTLCMD;
+	}
+	return 0;
+}
+
  long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  {
  	switch (cmd) {
@@ -4314,9 +4323,8 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  		cmd = FS_IOC_GETVERSION;
  		break;
  	case F2FS_IOC32_GARBAGE_COLLECT_RANGE:
-		return f2fs_compat_ioc_gc_range(file, arg);
  	case F2FS_IOC32_MOVE_RANGE:
-		return f2fs_compat_ioc_move_range(file, arg);
+		return __f2fs_compat_ioctl(file, cmd, arg);
  	case F2FS_IOC_START_ATOMIC_WRITE:
  	case F2FS_IOC_COMMIT_ATOMIC_WRITE:
  	case F2FS_IOC_START_VOLATILE_WRITE:

Thanks,

> 
> I feel that's still not entirely correct, because ENOTTY should take precedence
> over EIO or ENOSPC from the cp-related stuff.  But at least it would be
> consistent between the native and compat ioctls, and the cp-related checks
> wouldn't have to be duplicated in random ioctls...
> 
> - Eric
> .
>