Re: [PATCH v7] f2fs: support dynamic reserve/release for device aliasing

[Christophe JAILLET]

Le 06/08/2026 à 03:48, Daeho Jeong a écrit :
> From: Daeho Jeong <daehojeong@xxxxxxxxxx>
>
> This patch adds a dynamic management feature to the existing device
> aliasing functionality. It allows users to dynamically reserve or
> release specific devices from the filesystem's free pool at runtime
> through new ioctls.
>
> To support this, three new ioctls are introduced:
> - F2FS_IOC_RESERVE_DEV_ALIAS: This reclaims the space occupied by a
>    device aliasing file. It first performs a capacity check, resets GC
>    victim information for the target range, marks the segments as in-use
>    to prevent new allocations, and then triggers GC to migrate existing
>    valid data out of the range. Finally, it reserves these blocks in the
>    SIT to effectively exclude the device from the usable capacity.
>
> - F2FS_IOC_RELEASE_DEV_ALIAS: This releases the reserved space of a
>    previously reserved device aliasing file. It truncates the blocks
>    associated with the file, which makes them available for general
>    filesystem allocation again.
>
> - F2FS_IOC_GET_DEV_ALIAS_STATUS: This retrieves the current aliasing
>    status of a device aliasing file, returning whether the file is
>    released (inactive alias) or reserved (active alias, with blocks
>    fully allocated on the device).
>
> Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>

Hi,

this patch has already reached -next, but 2 comments below, should they 
make any sense.

> diff --git a/fs/f2fs/namei.c b/fs/f2fs/namei.c
> index cac03b8e91a1..8c3b57987f6c 100644
> --- a/fs/f2fs/namei.c
> +++ b/fs/f2fs/namei.c
> @@ -425,6 +425,9 @@ static int f2fs_link(struct dentry *old_dentry, struct inode *dir,
>   	if (!f2fs_is_checkpoint_ready(sbi))
>   		return -ENOSPC;
>   
> +	if (IS_DEVICE_ALIASING(inode))
> +		return -EPERM;
> +
>   	err = fscrypt_prepare_link(old_dentry, dir, dentry);
>   	if (err)
>   		return err;
> @@ -568,6 +571,9 @@ static int f2fs_unlink(struct inode *dir, struct dentry *dentry)
>   
>   	trace_f2fs_unlink_enter(dir, dentry);
>   
> +	if (IS_DEVICE_ALIASING(inode))
> +		return -EPERM;
> +

Based on surrounding goto, should this one be:
   err = -EPERM
   goto out;
?

>   	if (unlikely(f2fs_cp_error(sbi))) {
>   		err = -EIO;
>   		goto out;
> @@ -946,6 +952,9 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
>   	bool old_is_dir = S_ISDIR(old_inode->i_mode);
>   	int err;
>   
> +	if (IS_DEVICE_ALIASING(old_inode))
> +		return -EPERM;
> +
>   	if (unlikely(f2fs_cp_error(sbi)))
>   		return -EIO;
>   	if (!f2fs_is_checkpoint_ready(sbi))
> @@ -1016,6 +1025,8 @@ static int f2fs_rename(struct mnt_idmap *idmap, struct inode *old_dir,
>   	}
>   
>   	if (new_inode) {
> +		if (IS_DEVICE_ALIASING(new_inode))
> +			return -EPERM;

Based on surrounding goto, should this one be:
   err = -EPERM
   goto out_dir;
?

>   
>   		err = -ENOTEMPTY;
>   		if (old_is_dir && !f2fs_empty_dir(new_inode))
> @@ -1143,6 +1154,9 @@ static int f2fs_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
>   	int old_nlink = 0, new_nlink = 0;
>   	int err;
>   
> +	if (IS_DEVICE_ALIASING(old_inode) || IS_DEVICE_ALIASING(new_inode))
> +		return -EPERM;
> +
>   	if (unlikely(f2fs_cp_error(sbi)))
>   		return -EIO;
>   	if (!f2fs_is_checkpoint_ready(sbi))
[...]

CJ