Re: [f2fs-dev] [PATCH v6] f2fs: support dynamic reserve/release for device aliasing

Chao Yu <[email protected]> Tue, 4 Aug 2026 08:42:06 +0800
Newsgroups org.kernel.vger.linux-kernel,net.sourceforge.lists.linux-f2fs-devel
Message-ID <[email protected]>
On 8/4/26 00:18, Daeho Jeong wrote:
> On Sun, Aug 2, 2026 at 7:00 PM Chao Yu <[email protected]> wrote:
>>
>> On 7/30/26 23:46, Daeho Jeong wrote:
>>> From: Daeho Jeong <[email protected]>
>>>
>>> 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 <[email protected]>
>>> ---
>>> v6: fixed duplicated block reservations and racing w/ mmap.
>>>       added the extent alignment check for device aliasing areas.
>>> v5: prevented new segment allocation on devices undergoing reservation
>>>       or with active aliases.
>>>       used in-memory struct to reserve blocks for device aliasing.
>>>       cleared prefree (PRE) dirty segment bitmap.
>>> v4: renamed interfaces.
>>>       fixed race conditions between checkpoint=disable mount and ioctls.
>>>       refactored segment reservation part.
>>>       modified lock usage.
>>> v3: add CAP_SYS_ADMIN and checkpoint=disabled check.
>>>       remove a f2fs specific flag exposed with getflags.
>>> v2: prevent operations during checkpoint=disabled.
>>> ---
>>> ---
>>>    Documentation/filesystems/f2fs.rst |  35 ++++
>>>    fs/f2fs/data.c                     |   4 +-
>>>    fs/f2fs/extent_cache.c             |   7 +
>>>    fs/f2fs/f2fs.h                     |  19 +-
>>>    fs/f2fs/file.c                     | 273 ++++++++++++++++++++++++++++-
>>>    fs/f2fs/gc.c                       |  30 ++--
>>>    fs/f2fs/namei.c                    |  14 ++
>>>    fs/f2fs/segment.c                  | 176 +++++++++++++------
>>>    fs/f2fs/segment.h                  |  22 +++
>>>    fs/f2fs/super.c                    |  36 ++++
>>>    include/uapi/linux/f2fs.h          |   7 +
>>>    11 files changed, 555 insertions(+), 68 deletions(-)
>>>
>>> diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
>>> index 8c4a14ae444f..1a5fd4afe609 100644
>>> --- a/Documentation/filesystems/f2fs.rst
>>> +++ b/Documentation/filesystems/f2fs.rst
>>> @@ -1045,6 +1045,41 @@ So, the key idea is, user can do any file operations on /dev/vdc, and
>>>    reclaim the space after the use, while the space is counted as /data.
>>>    That doesn't require modifying partition size and filesystem format.
>>>
>>> +Dynamic Device Aliasing Management
>>> +----------------------------------
>>> +
>>> +In addition to static device aliasing by deleting the aliasing file, F2FS
>>> +supports dynamic management of device aliasing. This mechanism allows the system
>>> +to dynamically transition partition ownership between F2FS userdata and external
>>> +entities (e.g., zRAM, raw partition) based on system requirements without
>>> +deleting the master aliasing file or requiring unmount/remount.
>>> +
>>> +The master aliasing file is created during the initial format of the file system
>>> +and remains as a persistent control entity (ioctl gateway) in the root directory.
>>> +
>>> +- Partition Reservation (In-service to Aliased)
>>> +  When a specific partition needs to be dedicated to external services (e.g., zRAM),
>>> +  a user can reserve the device alias range via ioctl. The kernel resets GC victim
>>> +  information for the target range, marks segments as in-use to prevent new
>>> +  allocations, and triggers forced 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.
>>> +
>>> +- Partition Release (Aliased to In-service)
>>> +  When external usage concludes, the space is reclaimed not by deleting the file,
>>> +  but through the release ioctl. The kernel truncates blocks associated with
>>> +  the file, releasing them back to general filesystem allocation.
>>> +
>>> +.. code-block::
>>> +
>>> +   # f2fs_io dev_alias release /mnt/f2fs/vdc.file
>>> +   # df -h
>>> +   /dev/vdb                            64G  753M   64G   2% /mnt/f2fs
>>> +
>>> +   # f2fs_io dev_alias reserve /mnt/f2fs/vdc.file
>>> +   # df -h
>>> +   /dev/vdb                            64G   33G   32G  52% /mnt/f2fs
>>> +
>>>    Per-file Read-Only Large Folio Support
>>>    --------------------------------------
>>>
>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>> index ac1cf4de3d62..892d594048b7 100644
>>> --- a/fs/f2fs/data.c
>>> +++ b/fs/f2fs/data.c
>>> @@ -1270,7 +1270,7 @@ int f2fs_reserve_new_blocks(struct dnode_of_data *dn, blkcnt_t count)
>>>
>>>        if (unlikely(is_inode_flag_set(dn->inode, FI_NO_ALLOC)))
>>>                return -EPERM;
>>> -     err = inc_valid_block_count(sbi, dn->inode, &count, true);
>>> +     err = inc_valid_block_count(sbi, dn->inode, &count, true, false);
>>>        if (unlikely(err))
>>>                return err;
>>>
>>> @@ -1542,7 +1542,7 @@ static int __allocate_data_block(struct dnode_of_data *dn, int seg_type)
>>>
>>>        dn->data_blkaddr = f2fs_data_blkaddr(dn);
>>>        if (dn->data_blkaddr == NULL_ADDR) {
>>> -             err = inc_valid_block_count(sbi, dn->inode, &count, true);
>>> +             err = inc_valid_block_count(sbi, dn->inode, &count, true, false);
>>>                if (unlikely(err))
>>>                        return err;
>>>        }
>>> diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
>>> index 61f6b9714366..3a737db0c9e1 100644
>>> --- a/fs/f2fs/extent_cache.c
>>> +++ b/fs/f2fs/extent_cache.c
>>> @@ -62,6 +62,13 @@ bool sanity_check_extent_cache(struct inode *inode, struct folio *ifolio)
>>>                            __func__, inode->i_ino, ei.blk, ei.fofs, ei.len);
>>>                        return false;
>>>                }
>>> +
>>> +             if ((ei.blk % BLKS_PER_SEC(sbi)) || (ei.len % BLKS_PER_SEC(sbi))) {
>>> +                     f2fs_warn(sbi, "%s: device alias inode (ino=%llx)'s extent info [%u, %u, %u] is not aligned to section size %u",
>>> +                               __func__, inode->i_ino, ei.blk, ei.fofs, ei.len,
>>> +                               BLKS_PER_SEC(sbi));
>>> +                     return false;
>>> +             }
>>>                return true;
>>>        }
>>>
>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>> index f1774d4e18d2..f24e30bb5c3d 100644
>>> --- a/fs/f2fs/f2fs.h
>>> +++ b/fs/f2fs/f2fs.h
>>> @@ -1404,6 +1404,8 @@ struct f2fs_dev_info {
>>>        unsigned int total_segments;
>>>        block_t start_blk;
>>>        block_t end_blk;
>>> +     bool has_alias;
>>> +     bool is_reserving;
>>>    #ifdef CONFIG_BLK_DEV_ZONED
>>>        unsigned int nr_blkz;           /* Total number of zones */
>>>        unsigned long *blkz_seq;        /* Bitmap indicating sequential zones */
>>> @@ -1857,6 +1859,7 @@ struct f2fs_sb_info {
>>>        block_t last_valid_block_count;         /* for recovery */
>>>        block_t reserved_blocks;                /* configurable reserved blocks */
>>>        block_t current_reserved_blocks;        /* current reserved blocks */
>>> +     block_t alias_reserved_blocks;          /* reserved blocks for device alias */
>>>
>>>        /* Additional tracking for no checkpoint mode */
>>>        block_t unusable_block_count;           /* # of blocks saved by last cp */
>>> @@ -2559,7 +2562,8 @@ static inline unsigned int get_available_block_count(struct f2fs_sb_info *sbi,
>>>        block_t avail_user_block_count;
>>>
>>>        avail_user_block_count = sbi->user_block_count -
>>> -                                     sbi->current_reserved_blocks;
>>> +                                     sbi->current_reserved_blocks -
>>> +                                     sbi->alias_reserved_blocks;
>>>
>>>        if (test_opt(sbi, RESERVE_ROOT) && !__allow_reserved_root(sbi, inode, cap))
>>>                avail_user_block_count -= F2FS_OPTION(sbi).root_reserved_blocks;
>>> @@ -2576,7 +2580,8 @@ static inline unsigned int get_available_block_count(struct f2fs_sb_info *sbi,
>>>
>>>    static inline void f2fs_i_blocks_write(struct inode *, block_t, bool, bool);
>>>    static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
>>> -                              struct inode *inode, blkcnt_t *count, bool partial)
>>> +                              struct inode *inode, blkcnt_t *count,
>>> +                              bool partial, bool alias_reserved)
>>>    {
>>>        long long diff = 0, release = 0;
>>>        block_t avail_user_block_count;
>>> @@ -2599,10 +2604,16 @@ static inline int inc_valid_block_count(struct f2fs_sb_info *sbi,
>>>
>>>        spin_lock(&sbi->stat_lock);
>>>
>>> +     if (alias_reserved)
>>> +             sbi->alias_reserved_blocks -= *count;
>>> +
>>>        avail_user_block_count = get_available_block_count(sbi, inode, true);
>>>        diff = (long long)sbi->total_valid_block_count + *count -
>>>                                                avail_user_block_count;
>>>        if (unlikely(diff > 0)) {
>>> +             if (alias_reserved)
>>> +                     sbi->alias_reserved_blocks += *count;
>>> +
>>>                if (!partial) {
>>>                        spin_unlock(&sbi->stat_lock);
>>>                        release = *count;
>>> @@ -4010,6 +4021,8 @@ int f2fs_flush_device_cache(struct f2fs_sb_info *sbi);
>>>    void f2fs_destroy_flush_cmd_control(struct f2fs_sb_info *sbi, bool free);
>>>    void f2fs_invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr,
>>>                                                unsigned int len);
>>> +void f2fs_reserve_device_alias(struct f2fs_sb_info *sbi, block_t addr,
>>> +                                             unsigned int len);
>>>    bool f2fs_is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr);
>>>    int f2fs_start_discard_thread(struct f2fs_sb_info *sbi);
>>>    void f2fs_drop_discard_cmd(struct f2fs_sb_info *sbi);
>>> @@ -4231,6 +4244,8 @@ void f2fs_build_gc_manager(struct f2fs_sb_info *sbi);
>>>    int f2fs_gc_range(struct f2fs_sb_info *sbi,
>>>                unsigned int start_seg, unsigned int end_seg,
>>>                bool dry_run, unsigned int dry_run_sections);
>>> +void f2fs_reset_gc_victim_resource(struct f2fs_sb_info *sbi,
>>> +             unsigned int start, unsigned int end);
>>>    int f2fs_resize_fs(struct file *filp, __u64 block_count);
>>>    int __init f2fs_create_garbage_collection_cache(void);
>>>    void f2fs_destroy_garbage_collection_cache(void);
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 4b52c56d71f0..835f10bc59b5 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -813,13 +813,19 @@ int f2fs_do_truncate_blocks(struct inode *inode, u64 from, bool lock)
>>>
>>>        if (IS_DEVICE_ALIASING(inode)) {
>>>                struct extent_tree *et = F2FS_I(inode)->extent_tree[EX_READ];
>>> -             struct extent_info ei = et->largest;
>>> +             struct extent_info ei;
>>> +
>>> +             read_lock(&et->lock);
>>> +             ei = et->largest;
>>> +             read_unlock(&et->lock);
>>>
>>>                f2fs_invalidate_blocks(sbi, ei.blk, ei.len);
>>>
>>>                dec_valid_block_count(sbi, inode, ei.len);
>>>                f2fs_update_time(sbi, REQ_TIME);
>>>
>>> +             f2fs_drop_extent_tree(inode);
>>> +
>>>                f2fs_folio_put(ifolio, true);
>>>                goto out;
>>>        }
>>> @@ -1100,8 +1106,9 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
>>>        if ((attr->ia_valid & ATTR_SIZE)) {
>>>                if (mapping_large_folio_support(inode->i_mapping))
>>>                        return -EOPNOTSUPP;
>>> -             if (!f2fs_is_compress_backend_ready(inode) ||
>>> -                             IS_DEVICE_ALIASING(inode))
>>> +             if (IS_DEVICE_ALIASING(inode))
>>> +                     return -EPERM;
>>> +             if (!f2fs_is_compress_backend_ready(inode))
>>>                        return -EOPNOTSUPP;
>>>                if (is_inode_flag_set(inode, FI_COMPRESS_RELEASED) &&
>>>                        !IS_ALIGNED(attr->ia_size,
>>> @@ -2130,6 +2137,9 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
>>>        if (IS_NOQUOTA(inode))
>>>                return -EPERM;
>>>
>>> +     if (IS_DEVICE_ALIASING(inode))
>>> +             return -EPERM;
>>> +
>>>        if ((iflags ^ masked_flags) & F2FS_CASEFOLD_FL) {
>>>                if (!f2fs_sb_has_casefold(F2FS_I_SB(inode)))
>>>                        return -EOPNOTSUPP;
>>> @@ -2678,6 +2688,17 @@ static int f2fs_ioc_get_encryption_policy(struct file *filp, unsigned long arg)
>>>        return fscrypt_ioctl_get_policy(filp, (void __user *)arg);
>>>    }
>>>
>>> +static int f2fs_ioc_get_dev_alias_status(struct file *filp, unsigned long arg)
>>> +{
>>> +     struct inode *inode = file_inode(filp);
>>> +
>>> +     if (!IS_DEVICE_ALIASING(inode))
>>> +             return -EINVAL;
>>> +
>>> +     return put_user(F2FS_HAS_BLOCKS(inode) ? F2FS_DEV_ALIAS_STATUS_RESERVED :
>>> +                             F2FS_DEV_ALIAS_STATUS_RELEASED, (u32 __user *)arg);
>>> +}
>>> +
>>>    static int f2fs_ioc_get_encryption_pwsalt(struct file *filp, unsigned long arg)
>>>    {
>>>        struct inode *inode = file_inode(filp);
>>> @@ -3616,6 +3637,241 @@ static int f2fs_ioc_get_dev_alias_file(struct file *filp, unsigned long arg)
>>>                        (u32 __user *)arg);
>>>    }
>>>
>>> +static bool f2fs_get_dev_alias_extent(struct f2fs_sb_info *sbi,
>>> +                                    struct dentry *dentry,
>>> +                                    struct extent_info *ei)
>>> +{
>>> +     int i;
>>> +
>>> +     for (i = 1; i < sbi->s_ndevs; i++) {
>>> +             char *name = strrchr(FDEV(i).path, '/');
>>> +
>>> +             name = name ? name + 1 : FDEV(i).path;
>>> +             if (strcmp(name, dentry->d_name.name))
>>> +                     continue;
>>> +
>>> +             ei->blk = FDEV(i).start_blk;
>>> +             ei->len = FDEV(i).total_segments << sbi->log_blocks_per_seg;
>>> +             ei->fofs = 0;
>>> +             return true;
>>> +     }
>>> +     return false;
>>> +}
>>> +
>>> +static int f2fs_ioc_reserve_dev_alias(struct file *filp)
>>> +{
>>> +     struct inode *inode = file_inode(filp);
>>> +     struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>> +     struct extent_tree *et = F2FS_I(inode)->extent_tree[EX_READ];
>>> +     struct extent_info ei;
>>> +     struct cp_control cpc = { CP_SYNC, 0, 0, 0 };
>>> +     struct f2fs_lock_context lc, glc;
>>> +     blkcnt_t count;
>>> +     unsigned int start, end;
>>> +     int type, err;
>>> +
>>> +     if (!capable(CAP_SYS_ADMIN))
>>> +             return -EPERM;
>>> +
>>> +     if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED)))
>>> +             return -EINVAL;
>>> +
>>> +     err = mnt_want_write_file(filp);
>>> +     if (err)
>>> +             return err;
>>> +
>>> +     inode_lock(inode);
>>> +
>>> +     if (!IS_DEVICE_ALIASING(inode)) {
>>> +             err = -EINVAL;
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     if (F2FS_HAS_BLOCKS(inode)) {
>>> +             err = 0;
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     if (!f2fs_get_dev_alias_extent(sbi, filp->f_path.dentry, &ei)) {
>>> +             f2fs_warn(sbi, "device alias file (%s, ino=%llu) has no matching device",
>>> +                       filp->f_path.dentry->d_name.name,
>>> +                       (unsigned long long)inode->i_ino);
>>> +             set_sbi_flag(sbi, SBI_NEED_FSCK);
>>> +             f2fs_handle_error(sbi, ERROR_CORRUPTED_INODE);
>>> +             err = -EFSCORRUPTED;
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     spin_lock(&sbi->stat_lock);
>>> +     if (sbi->total_valid_block_count + ei.len >
>>> +                     get_available_block_count(sbi, inode, true)) {
>>> +             spin_unlock(&sbi->stat_lock);
>>> +             err = -ENOSPC;
>>> +             goto out_inode_unlock;
>>> +     }
>>> +     sbi->alias_reserved_blocks += ei.len;
>>> +     spin_unlock(&sbi->stat_lock);
>>> +
>>> +     spin_lock(&FREE_I(sbi)->segmap_lock);
>>> +     FDEV(f2fs_target_device_index(sbi, ei.blk)).is_reserving = true;
>>> +     spin_unlock(&FREE_I(sbi)->segmap_lock);
>>> +
>>> +     start = GET_SEGNO(sbi, ei.blk);
>>> +     end = GET_SEGNO(sbi, ei.blk + ei.len - 1);
>>> +
>>> +     /* Acquire gc_lock for victim reset, curseg resize, and range GC */
>>> +     f2fs_down_write_trace(&sbi->gc_lock, &glc);
>>> +
>>> +     /* Reset the victim information to prevent GC from targeting the range */
>>> +     f2fs_reset_gc_victim_resource(sbi, start, end);
>>> +
>>> +     /* Move out cursegs from the target range */
>>> +     for (type = CURSEG_HOT_DATA; type < NR_CURSEG_PERSIST_TYPE; type++) {
>>> +             err = f2fs_allocate_segment_for_resize(sbi, type, start, end);
>>> +             if (err)
>>> +                     goto out_gc_unlock;
>>> +     }
>>> +
>>> +     f2fs_lock_op(sbi, &lc);
>>> +
>>> +     if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
>>> +             err = -EINVAL;
>>> +             f2fs_unlock_op(sbi, &lc);
>>> +             goto out_gc_unlock;
>>> +     }
>>> +
>>> +     /* do GC to move out valid blocks in the range all at once! */
>>> +     err = f2fs_gc_range(sbi, start, end, false, 0);
>>> +     if (err) {
>>> +             f2fs_unlock_op(sbi, &lc);
>>> +             goto out_gc_unlock;
>>> +     }
>>> +
>>> +     count = ei.len;
>>> +     err = inc_valid_block_count(sbi, inode, &count, false, true);
>>> +     if (err) {
>>> +             f2fs_unlock_op(sbi, &lc);
>>> +             goto out_gc_unlock;
>>> +     }
>>> +
>>> +     write_lock(&et->lock);
>>> +     et->largest = ei;
>>> +     write_unlock(&et->lock);
>>> +     clear_inode_flag(inode, FI_NO_EXTENT);
>>> +
>>> +     f2fs_reserve_device_alias(sbi, ei.blk, ei.len);
>>> +
>>> +     i_size_write(inode, (loff_t)ei.len << sbi->log_blocksize);
>>> +     f2fs_update_inode_page(inode);
>>> +
>>> +     spin_lock(&FREE_I(sbi)->segmap_lock);
>>> +     FDEV(f2fs_target_device_index(sbi, ei.blk)).is_reserving = false;
>>> +     spin_unlock(&FREE_I(sbi)->segmap_lock);
>>> +
>>> +     f2fs_unlock_op(sbi, &lc);
>>> +     f2fs_up_write_trace(&sbi->gc_lock, &glc);
>>
>> Do we need to call f2fs_write_checkpoint(sbi, &cpc) here to make sure persist
>> device alias file first? to avoid following f2fs_ioc_release_dev_alias() racin
>>    w/ f2fs_ioc_reserve_dev_alias()?
>>
>> - f2fs_ioc_reserve_dev_alias            - f2fs_ioc_release_dev_alias
>> ...
>>    - f2fs_unlock_op
>>    - f2fs_up_write_trace(gc_lock)
>>    - inode_unlock
>>                                           - inode_lock
>>                                           ...
>>    - f2fs_write_checkpoint
> 
> Hi Chao,
> 
> I couldn't get your point. Could you elaborate more, if I missed it?

Hi Daeho,

Actually, what I mean is if f2fs_write_checkpoint() is not covered by
inode lock, in race condition there will be below invoking serial:

Assume:
f2fs_ioc_reserve_dev_alias := reserve_dev_alias + f2fs_write_checkpoint
f2fs_ioc_release_dev_alias := release_dev_alias + f2fs_write_checkpoint

1) Thread A: reserve_dev_alias
2) Thread B: release_dev_alias
3) Thread C: reserve_dev_alias
4) Thread B: f2fs_write_checkpoint
5) Thread A: f2fs_write_checkpoint
6) Thread C: f2fs_write_checkpoint

After 1) all data after reserve_dev_alias() are not checkpointed, then the
following release_dev_alias in 2) won't encounter any issue, right? and the
same quetions for 3).

IOW, reserve_dev_alias/release_dev_alias doesn't need to rely on checkpointed
state of each other, am I understand it correctly? if so there won't be any
issue.

> 
> 1. In-memory state is already atomic (No Race):
>      Before inode_unlock(), all in-memory metadata (extent_tree, SIT
> segment bitmaps, i_size, and dirty inode page) are fully updated under
> inode_lock + f2fs_lock_op. A subsequent f2fs_ioc_release_dev_alias()
> will observe a complete, consistent state.
> 
> 2. On-disk consistency & crash safety:
>      Checkpoints are serialized internally via cp_mutex /
> f2fs_lock_all(). Regardless of the checkpoint execution timing or any
> sudden power-off (SPO) between the two ioctls, the filesystem always
> recovers to the last committed atomic checkpoint without metadata
> corruption.

Thanks for the explanation.

Thanks,

> 
> Thanks,
> 
>>
>>> +
>>> +     inode_unlock(inode);
>>> +     mnt_drop_write_file(filp);
>>> +
>>> +     return f2fs_write_checkpoint(sbi, &cpc);
>>> +
>>> +out_gc_unlock:
>>> +     spin_lock(&sbi->stat_lock);
>>> +     sbi->alias_reserved_blocks -= ei.len;
>>> +     spin_unlock(&sbi->stat_lock);
>>> +
>>> +     spin_lock(&FREE_I(sbi)->segmap_lock);
>>> +     FDEV(f2fs_target_device_index(sbi, ei.blk)).is_reserving = false;
>>> +     spin_unlock(&FREE_I(sbi)->segmap_lock);
>>> +     f2fs_up_write_trace(&sbi->gc_lock, &glc);
>>> +
>>> +out_inode_unlock:
>>> +     inode_unlock(inode);
>>> +     mnt_drop_write_file(filp);
>>> +     return err;
>>> +}
>>> +
>>> +static int f2fs_ioc_release_dev_alias(struct file *filp)
>>> +{
>>> +     struct inode *inode = file_inode(filp);
>>> +     struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
>>> +     struct extent_tree *et = F2FS_I(inode)->extent_tree[EX_READ];
>>> +     struct extent_info ei = {0, };
>>> +     struct cp_control cpc = { CP_SYNC, 0, 0, 0 };
>>> +     struct f2fs_lock_context lc, glc;
>>> +     int err;
>>> +
>>> +     if (!capable(CAP_SYS_ADMIN))
>>> +             return -EPERM;
>>> +
>>> +     if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED)))
>>> +             return -EINVAL;
>>> +
>>> +     err = mnt_want_write_file(filp);
>>> +     if (err)
>>> +             return err;
>>> +
>>> +     inode_lock(inode);
>>> +
>>> +     if (!IS_DEVICE_ALIASING(inode)) {
>>> +             err = -EINVAL;
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     if (!F2FS_HAS_BLOCKS(inode)) {
>>> +             err = 0;
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     err = filemap_write_and_wait(inode->i_mapping);
>>> +     if (err)
>>> +             goto out_inode_unlock;
>>> +
>>> +     read_lock(&et->lock);
>>> +     ei = et->largest;
>>> +     read_unlock(&et->lock);
>>> +
>>> +     f2fs_down_write_trace(&sbi->gc_lock, &glc);
>>> +     f2fs_lock_op(sbi, &lc);
>>> +
>>> +     if (unlikely(is_sbi_flag_set(sbi, SBI_CP_DISABLED))) {
>>> +             err = -EINVAL;
>>> +             f2fs_unlock_op(sbi, &lc);
>>> +             f2fs_up_write_trace(&sbi->gc_lock, &glc);
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     filemap_invalidate_lock(inode->i_mapping);
>>> +     truncate_setsize(inode, 0);
>>> +
>>> +     err = f2fs_truncate_blocks(inode, 0, false);
>>> +     if (err)
>>> +             i_size_write(inode, (loff_t)ei.len << sbi->log_blocksize);
>>> +     filemap_invalidate_unlock(inode->i_mapping);
>>> +
>>> +     if (err) {
>>> +             f2fs_unlock_op(sbi, &lc);
>>> +             f2fs_up_write_trace(&sbi->gc_lock, &glc);
>>> +             goto out_inode_unlock;
>>> +     }
>>> +
>>> +     f2fs_update_inode_page(inode);
>>> +
>>> +     f2fs_unlock_op(sbi, &lc);
>>> +     f2fs_up_write_trace(&sbi->gc_lock, &glc);
>>
>>          err = f2fs_write_checkpoint(sbi, &cpc);
>>
>> Thanks,
>>
>>> +
>>> +     inode_unlock(inode);
>>> +     mnt_drop_write_file(filp);
>>> +
>>> +     return f2fs_write_checkpoint(sbi, &cpc);
>>> +
>>> +out_inode_unlock:
>>> +     inode_unlock(inode);
>>> +     mnt_drop_write_file(filp);
>>> +     return err;
>>> +}
>>> +
>>>    static int f2fs_ioc_io_prio(struct file *filp, unsigned long arg)
>>>    {
>>>        struct inode *inode = file_inode(filp);
>>> @@ -4041,7 +4297,7 @@ static int reserve_compress_blocks(struct dnode_of_data *dn, pgoff_t count,
>>>                }
>>>
>>>                ret = inc_valid_block_count(sbi, dn->inode,
>>> -                                             &to_reserved, false);
>>> +                                             &to_reserved, false, false);
>>>                if (unlikely(ret))
>>>                        return ret;
>>>
>>> @@ -4742,8 +4998,14 @@ static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>>>                return f2fs_ioc_compress_file(filp);
>>>        case F2FS_IOC_GET_DEV_ALIAS_FILE:
>>>                return f2fs_ioc_get_dev_alias_file(filp, arg);
>>> +     case F2FS_IOC_GET_DEV_ALIAS_STATUS:
>>> +             return f2fs_ioc_get_dev_alias_status(filp, arg);
>>>        case F2FS_IOC_IO_PRIO:
>>>                return f2fs_ioc_io_prio(filp, arg);
>>> +     case F2FS_IOC_RESERVE_DEV_ALIAS:
>>> +             return f2fs_ioc_reserve_dev_alias(filp);
>>> +     case F2FS_IOC_RELEASE_DEV_ALIAS:
>>> +             return f2fs_ioc_release_dev_alias(filp);
>>>        default:
>>>                return -ENOTTY;
>>>        }
>>> @@ -5530,7 +5792,10 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>>>        case F2FS_IOC_DECOMPRESS_FILE:
>>>        case F2FS_IOC_COMPRESS_FILE:
>>>        case F2FS_IOC_GET_DEV_ALIAS_FILE:
>>> +     case F2FS_IOC_GET_DEV_ALIAS_STATUS:
>>>        case F2FS_IOC_IO_PRIO:
>>> +     case F2FS_IOC_RESERVE_DEV_ALIAS:
>>> +     case F2FS_IOC_RELEASE_DEV_ALIAS:
>>>                break;
>>>        default:
>>>                return -ENOIOCTLCMD;
>>> diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
>>> index ffaa7ba76a1b..93bcb35a5b5d 100644
>>> --- a/fs/f2fs/gc.c
>>> +++ b/fs/f2fs/gc.c
>>> @@ -2197,29 +2197,37 @@ int f2fs_gc_range(struct f2fs_sb_info *sbi,
>>>        return 0;
>>>    }
>>>
>>> +void f2fs_reset_gc_victim_resource(struct f2fs_sb_info *sbi,
>>> +                     unsigned int start, unsigned int end)
>>> +{
>>> +     int i;
>>> +
>>> +     mutex_lock(&DIRTY_I(sbi)->seglist_lock);
>>> +     for (i = 0; i < MAX_GC_POLICY; i++)
>>> +             if (SIT_I(sbi)->last_victim[i] >= start &&
>>> +                     SIT_I(sbi)->last_victim[i] <= end)
>>> +                     SIT_I(sbi)->last_victim[i] = 0;
>>> +
>>> +     for (i = BG_GC; i <= FG_GC; i++)
>>> +             if (sbi->next_victim_seg[i] >= start &&
>>> +                     sbi->next_victim_seg[i] <= end)
>>> +                     sbi->next_victim_seg[i] = NULL_SEGNO;
>>> +     mutex_unlock(&DIRTY_I(sbi)->seglist_lock);
>>> +}
>>> +
>>>    static int free_segment_range(struct f2fs_sb_info *sbi,
>>>                                unsigned int secs, bool dry_run)
>>>    {
>>>        unsigned int next_inuse, start, end;
>>>        struct cp_control cpc = { CP_RESIZE, 0, 0, 0 };
>>> -     int gc_mode, gc_type;
>>>        int err = 0;
>>>        int type;
>>>
>>> -     /* Force block allocation for GC */
>>>        MAIN_SECS(sbi) -= secs;
>>>        start = MAIN_SECS(sbi) * SEGS_PER_SEC(sbi);
>>>        end = MAIN_SEGS(sbi) - 1;
>>>
>>> -     mutex_lock(&DIRTY_I(sbi)->seglist_lock);
>>> -     for (gc_mode = 0; gc_mode < MAX_GC_POLICY; gc_mode++)
>>> -             if (SIT_I(sbi)->last_victim[gc_mode] >= start)
>>> -                     SIT_I(sbi)->last_victim[gc_mode] = 0;
>>> -
>>> -     for (gc_type = BG_GC; gc_type <= FG_GC; gc_type++)
>>> -             if (sbi->next_victim_seg[gc_type] >= start)
>>> -                     sbi->next_victim_seg[gc_type] = NULL_SEGNO;
>>> -     mutex_unlock(&DIRTY_I(sbi)->seglist_lock);
>>> +     f2fs_reset_gc_victim_resource(sbi, start, end);
>>>
>>>        /* Move out cursegs from the target range */
>>>        for (type = CURSEG_HOT_DATA; type < NR_CURSEG_PERSIST_TYPE; type++) {
>>> 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;
>>> +
>>>        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;
>>>
>>>                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))
>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>> index d71ddb3ee918..d70dc5ef3de4 100644
>>> --- a/fs/f2fs/segment.c
>>> +++ b/fs/f2fs/segment.c
>>> @@ -261,7 +261,7 @@ static int __replace_atomic_write_block(struct inode *inode, pgoff_t index,
>>>        } else {
>>>                blkcnt_t count = 1;
>>>
>>> -             err = inc_valid_block_count(sbi, inode, &count, true);
>>> +             err = inc_valid_block_count(sbi, inode, &count, true, false);
>>>                if (err) {
>>>                        f2fs_put_dnode(&dn);
>>>                        return err;
>>> @@ -2502,35 +2502,42 @@ static int update_sit_entry_for_alloc(struct f2fs_sb_info *sbi, struct seg_entry
>>>                                unsigned int segno, block_t blkaddr, unsigned int offset, int del)
>>>    {
>>>        bool exist;
>>> +     int del_count = del;
>>> +     int i;
>>>
>>> -     exist = f2fs_test_and_set_bit(offset, se->cur_valid_map);
>>> -     if (unlikely(exist)) {
>>> -             f2fs_err(sbi, "Bitmap was wrongly set, blk:%u", blkaddr);
>>> -             f2fs_bug_on(sbi, 1);
>>> -             se->valid_blocks--;
>>> -             del = 0;
>>> -     }
>>> +     f2fs_bug_on(sbi, GET_SEGNO(sbi, blkaddr) != GET_SEGNO(sbi, blkaddr + del_count - 1));
>>>
>>> -     if (f2fs_block_unit_discard(sbi) &&
>>> -                     !f2fs_test_and_set_bit(offset, se->discard_map))
>>> -             sbi->discard_blks--;
>>> +     for (i = 0; i < del_count; i++) {
>>> +             exist = f2fs_test_and_set_bit(offset + i, se->cur_valid_map);
>>> +             if (unlikely(exist)) {
>>> +                     f2fs_err(sbi, "Bitmap was wrongly set, blk:%u", blkaddr + i);
>>> +                     f2fs_bug_on(sbi, 1);
>>> +                     se->valid_blocks--;
>>> +                     del -= 1;
>>> +                     continue;
>>> +             }
>>>
>>> -     /*
>>> -      * SSR should never reuse block which is checkpointed
>>> -      * or newly invalidated.
>>> -      */
>>> -     if (!is_sbi_flag_set(sbi, SBI_CP_DISABLED)) {
>>> -             if (!f2fs_test_and_set_bit(offset, se->ckpt_valid_map)) {
>>> -                     se->ckpt_valid_blocks++;
>>> -                     if (__is_large_section(sbi))
>>> -                             get_sec_entry(sbi, segno)->ckpt_valid_blocks++;
>>> +             if (f2fs_block_unit_discard(sbi) &&
>>> +                             !f2fs_test_and_set_bit(offset + i, se->discard_map))
>>> +                     sbi->discard_blks--;
>>> +
>>> +             /*
>>> +              * SSR should never reuse block which is checkpointed
>>> +              * or newly invalidated.
>>> +              */
>>> +             if (!is_sbi_flag_set(sbi, SBI_CP_DISABLED)) {
>>> +                     if (!f2fs_test_and_set_bit(offset + i, se->ckpt_valid_map)) {
>>> +                             se->ckpt_valid_blocks++;
>>> +                             if (__is_large_section(sbi))
>>> +                                     get_sec_entry(sbi, segno)->ckpt_valid_blocks++;
>>> +                     }
>>>                }
>>> -     }
>>>
>>> -     if (!f2fs_test_bit(offset, se->ckpt_valid_map)) {
>>> -             se->ckpt_valid_blocks += del;
>>> -             if (__is_large_section(sbi))
>>> -                     get_sec_entry(sbi, segno)->ckpt_valid_blocks += del;
>>> +             if (!f2fs_test_bit(offset + i, se->ckpt_valid_map)) {
>>> +                     se->ckpt_valid_blocks += 1;
>>> +                     if (__is_large_section(sbi))
>>> +                             get_sec_entry(sbi, segno)->ckpt_valid_blocks += 1;
>>> +             }
>>>        }
>>>
>>>        if (__is_large_section(sbi))
>>> @@ -2585,9 +2592,14 @@ void f2fs_invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr,
>>>        unsigned int segno = GET_SEGNO(sbi, addr);
>>>        struct sit_info *sit_i = SIT_I(sbi);
>>>        block_t addr_start = addr, addr_end = addr + len - 1;
>>> -     unsigned int seg_num = GET_SEGNO(sbi, addr_end) - segno + 1;
>>> +     unsigned int seg_num;
>>>        unsigned int i = 1, max_blocks = sbi->blocks_per_seg, cnt;
>>>
>>> +     if (len == 0)
>>> +             return;
>>> +
>>> +     seg_num = GET_SEGNO(sbi, addr_end) - segno + 1;
>>> +
>>>        f2fs_bug_on(sbi, addr == NULL_ADDR);
>>>        if (addr == NEW_ADDR || addr == COMPRESS_ADDR)
>>>                return;
>>> @@ -2620,6 +2632,52 @@ void f2fs_invalidate_blocks(struct f2fs_sb_info *sbi, block_t addr,
>>>        up_write(&sit_i->sentry_lock);
>>>    }
>>>
>>> +void f2fs_reserve_device_alias(struct f2fs_sb_info *sbi, block_t addr,
>>> +                             unsigned int len)
>>> +{
>>> +     unsigned int segno = GET_SEGNO(sbi, addr);
>>> +     struct sit_info *sit_i = SIT_I(sbi);
>>> +     block_t addr_start = addr, addr_end = addr + len - 1;
>>> +     unsigned int seg_num;
>>> +     unsigned int i = 1, max_blocks = sbi->blocks_per_seg, cnt;
>>> +
>>> +     if (len == 0)
>>> +             return;
>>> +
>>> +     seg_num = GET_SEGNO(sbi, addr_end) - segno + 1;
>>> +
>>> +     down_write(&sit_i->sentry_lock);
>>> +
>>> +     if (seg_num == 1)
>>> +             cnt = len;
>>> +     else
>>> +             cnt = max_blocks - GET_BLKOFF_FROM_SEG0(sbi, addr);
>>> +
>>> +     do {
>>> +             update_segment_mtime(sbi, addr_start, 0);
>>> +             update_sit_entry(sbi, addr_start, cnt);
>>> +             __set_test_and_inuse(sbi, segno);
>>> +
>>> +             /* Remove the segment from PRE (prefree) to prevent checkpoint from freeing it! */
>>> +             mutex_lock(&DIRTY_I(sbi)->seglist_lock);
>>> +             if (test_and_clear_bit(segno, DIRTY_I(sbi)->dirty_segmap[PRE]))
>>> +                     DIRTY_I(sbi)->nr_dirty[PRE]--;
>>> +             mutex_unlock(&DIRTY_I(sbi)->seglist_lock);
>>> +
>>> +             /* add it into dirty seglist */
>>> +             locate_dirty_segment(sbi, segno);
>>> +
>>> +             /* update @addr_start and @cnt and @segno */
>>> +             addr_start = START_BLOCK(sbi, ++segno);
>>> +             if (++i == seg_num)
>>> +                     cnt = GET_BLKOFF_FROM_SEG0(sbi, addr_end) + 1;
>>> +             else
>>> +                     cnt = max_blocks;
>>> +     } while (i <= seg_num);
>>> +
>>> +     up_write(&sit_i->sentry_lock);
>>> +}
>>> +
>>>    bool f2fs_is_checkpointed_data(struct f2fs_sb_info *sbi, block_t blkaddr)
>>>    {
>>>        struct sit_info *sit_i = SIT_I(sbi);
>>> @@ -2758,8 +2816,13 @@ static int is_next_segment_free(struct f2fs_sb_info *sbi,
>>>        unsigned int segno = curseg->segno + 1;
>>>        struct free_segmap_info *free_i = FREE_I(sbi);
>>>
>>> -     if (segno < MAIN_SEGS(sbi) && segno % SEGS_PER_SEC(sbi))
>>> +     if (segno < MAIN_SEGS(sbi) && segno % SEGS_PER_SEC(sbi)) {
>>> +             int devi = f2fs_target_device_index(sbi, START_BLOCK(sbi, segno));
>>> +
>>> +             if (f2fs_dev_is_reserving(sbi, devi))
>>> +                     return 0;
>>>                return !test_bit(segno, free_i->free_segmap);
>>> +     }
>>>        return 0;
>>>    }
>>>
>>> @@ -2778,7 +2841,8 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
>>>        unsigned int alloc_policy = sbi->allocate_section_policy;
>>>        unsigned int alloc_hint = sbi->allocate_section_hint;
>>>        bool init = true;
>>> -     int i;
>>> +     bool looped = false;
>>> +     int i, devi;
>>>        int ret = 0;
>>>
>>>        spin_lock(&free_i->segmap_lock);
>>> @@ -2791,8 +2855,13 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
>>>        if (!new_sec && ((*newseg + 1) % SEGS_PER_SEC(sbi))) {
>>>                segno = find_next_zero_bit(free_i->free_segmap,
>>>                        GET_SEG_FROM_SEC(sbi, hint + 1), *newseg + 1);
>>> -             if (segno < GET_SEG_FROM_SEC(sbi, hint + 1))
>>> +             if (segno < GET_SEG_FROM_SEC(sbi, hint + 1)) {
>>> +                     devi = f2fs_target_device_index(sbi, START_BLOCK(sbi, segno));
>>> +
>>> +                     if (f2fs_dev_is_alloc_blocked(sbi, devi, pinning))
>>> +                             goto find_other_zone;
>>>                        goto got_it;
>>> +             }
>>>        }
>>>
>>>    #ifdef CONFIG_BLK_DEV_ZONED
>>> @@ -2828,33 +2897,42 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
>>>    find_other_zone:
>>>        secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), hint);
>>>
>>> -#ifdef CONFIG_BLK_DEV_ZONED
>>> -     if (secno >= MAIN_SECS(sbi) && f2fs_sb_has_blkzoned(sbi)) {
>>> -             /* Write only to sequential zones */
>>> -             if (sbi->blkzone_alloc_policy == BLKZONE_ALLOC_ONLY_SEQ) {
>>> -                     hint = GET_SEC_FROM_SEG(sbi, sbi->first_seq_zone_segno);
>>> -                     secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), hint);
>>> -             } else
>>> -                     secno = find_first_zero_bit(free_i->free_secmap,
>>> -                                                             MAIN_SECS(sbi));
>>> -             if (secno >= MAIN_SECS(sbi)) {
>>> -                     ret = -ENOSPC;
>>> -                     f2fs_bug_on(sbi, 1);
>>> -                     goto out_unlock;
>>> -             }
>>> -     }
>>> -#endif
>>> -
>>>        if (secno >= MAIN_SECS(sbi)) {
>>> -             secno = find_first_zero_bit(free_i->free_secmap,
>>> -                                                     MAIN_SECS(sbi));
>>> -             if (secno >= MAIN_SECS(sbi)) {
>>> +             if (looped) {
>>>                        ret = -ENOSPC;
>>>                        f2fs_bug_on(sbi, !pinning);
>>>                        goto out_unlock;
>>>                }
>>> +             hint = 0;
>>> +#ifdef CONFIG_BLK_DEV_ZONED
>>> +             /* Write only to sequential zones */
>>> +             if (f2fs_sb_has_blkzoned(sbi) &&
>>> +                     sbi->blkzone_alloc_policy == BLKZONE_ALLOC_ONLY_SEQ)
>>> +                     hint = GET_SEC_FROM_SEG(sbi, sbi->first_seq_zone_segno);
>>> +#endif
>>> +             looped = true;
>>> +             goto find_other_zone;
>>>        }
>>> +
>>>        segno = GET_SEG_FROM_SEC(sbi, secno);
>>> +
>>> +     devi = f2fs_target_device_index(sbi, START_BLOCK(sbi, segno));
>>> +
>>> +     if (f2fs_dev_is_alloc_blocked(sbi, devi, pinning)) {
>>> +             while (devi < sbi->s_ndevs &&
>>> +                     f2fs_dev_is_alloc_blocked(sbi, devi, pinning)) {
>>> +                     unsigned int end_segno = GET_SEGNO(sbi, FDEV(devi).end_blk);
>>> +
>>> +                     hint = GET_SEC_FROM_SEG(sbi, end_segno) + 1;
>>> +                     devi++;
>>> +             }
>>> +             goto find_other_zone;
>>> +     }
>>> +
>>> +     if (sec_usage_check(sbi, secno)) {
>>> +             hint = secno + 1;
>>> +             goto find_other_zone;
>>> +     }
>>>        zoneno = GET_ZONE_FROM_SEC(sbi, secno);
>>>
>>>        /* give up on finding another zone */
>>> diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
>>> index b0c06b3580b4..107508ae7eb3 100644
>>> --- a/fs/f2fs/segment.h
>>> +++ b/fs/f2fs/segment.h
>>> @@ -954,10 +954,32 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type)
>>>                                - (base + 1) + type;
>>>    }
>>>
>>> +static inline bool f2fs_dev_is_reserving(struct f2fs_sb_info *sbi, int devi)
>>> +{
>>> +     if (!f2fs_sb_has_device_alias(sbi))
>>> +             return false;
>>> +     return FDEV(devi).is_reserving;
>>> +}
>>> +
>>> +static inline bool f2fs_dev_is_alloc_blocked(struct f2fs_sb_info *sbi,
>>> +                                     int devi, bool pinning)
>>> +{
>>> +     if (!f2fs_sb_has_device_alias(sbi))
>>> +             return false;
>>> +     return (pinning && FDEV(devi).has_alias) || FDEV(devi).is_reserving;
>>> +}
>>> +
>>>    static inline bool sec_usage_check(struct f2fs_sb_info *sbi, unsigned int secno)
>>>    {
>>>        if (is_cursec(sbi, secno) || (sbi->cur_victim_sec == secno))
>>>                return true;
>>> +     if (f2fs_sb_has_device_alias(sbi)) {
>>> +             block_t start_blk = START_BLOCK(sbi, GET_SEG_FROM_SEC(sbi, secno));
>>> +             int devi = f2fs_target_device_index(sbi, start_blk);
>>> +
>>> +             if (f2fs_dev_is_reserving(sbi, devi))
>>> +                     return true;
>>> +     }
>>>        return false;
>>>    }
>>>
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index c448d992ff2a..d5dc83e613e2 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -5001,6 +5001,39 @@ static void f2fs_tuning_parameters(struct f2fs_sb_info *sbi)
>>>        sbi->readdir_ra = true;
>>>    }
>>>
>>> +static void f2fs_restore_device_alias(struct f2fs_sb_info *sbi)
>>> +{
>>> +     struct inode *root = d_inode(sbi->sb->s_root);
>>> +     struct f2fs_dir_entry *de;
>>> +     struct folio *folio;
>>> +     int i;
>>> +
>>> +     if (!f2fs_sb_has_device_alias(sbi))
>>> +             return;
>>> +
>>> +     for (i = 1; i < sbi->s_ndevs; i++) {
>>> +             char *name = strrchr(FDEV(i).path, '/');
>>> +             struct inode *inode;
>>> +             struct qstr qstr;
>>> +
>>> +             name = name ? name + 1 : FDEV(i).path;
>>> +             qstr.name = name;
>>> +             qstr.len = strlen(name);
>>> +
>>> +             de = f2fs_find_entry(root, &qstr, &folio);
>>> +             if (!de)
>>> +                     continue;
>>> +
>>> +             inode = f2fs_iget(sbi->sb, le32_to_cpu(de->ino));
>>> +             if (!IS_ERR(inode)) {
>>> +                     if (IS_DEVICE_ALIASING(inode))
>>> +                             FDEV(i).has_alias = true;
>>> +                     iput(inode);
>>> +             }
>>> +             f2fs_folio_put(folio, 0);
>>> +     }
>>> +}
>>> +
>>>    static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
>>>    {
>>>        struct f2fs_fs_context *ctx = fc->fs_private;
>>> @@ -5209,6 +5242,7 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
>>>        sbi->last_valid_block_count = sbi->total_valid_block_count;
>>>        sbi->reserved_blocks = 0;
>>>        sbi->current_reserved_blocks = 0;
>>> +     sbi->alias_reserved_blocks = 0;
>>>        limit_reserve_root(sbi);
>>>        adjust_unusable_cap_perc(sbi);
>>>
>>> @@ -5436,6 +5470,8 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
>>>        f2fs_update_time(sbi, REQ_TIME);
>>>        clear_sbi_flag(sbi, SBI_CP_DISABLED_QUICK);
>>>
>>> +     f2fs_restore_device_alias(sbi);
>>> +
>>>        sbi->umount_lock_holder = NULL;
>>>        return 0;
>>>
>>> diff --git a/include/uapi/linux/f2fs.h b/include/uapi/linux/f2fs.h
>>> index 795e26258355..4409ada2fecb 100644
>>> --- a/include/uapi/linux/f2fs.h
>>> +++ b/include/uapi/linux/f2fs.h
>>> @@ -45,6 +45,9 @@
>>>    #define F2FS_IOC_START_ATOMIC_REPLACE       _IO(F2FS_IOCTL_MAGIC, 25)
>>>    #define F2FS_IOC_GET_DEV_ALIAS_FILE _IOR(F2FS_IOCTL_MAGIC, 26, __u32)
>>>    #define F2FS_IOC_IO_PRIO            _IOW(F2FS_IOCTL_MAGIC, 27, __u32)
>>> +#define F2FS_IOC_RESERVE_DEV_ALIAS   _IO(F2FS_IOCTL_MAGIC, 28)
>>> +#define F2FS_IOC_RELEASE_DEV_ALIAS   _IO(F2FS_IOCTL_MAGIC, 29)
>>> +#define F2FS_IOC_GET_DEV_ALIAS_STATUS        _IOR(F2FS_IOCTL_MAGIC, 30, __u32)
>>>
>>>    /*
>>>     * should be same as XFS_IOC_GOINGDOWN.
>>> @@ -70,6 +73,10 @@ enum {
>>>        F2FS_IOPRIO_MAX,
>>>    };
>>>
>>> +/* for F2FS_IOC_GET_DEV_ALIAS_STATUS */
>>> +#define F2FS_DEV_ALIAS_STATUS_RELEASED       0
>>> +#define F2FS_DEV_ALIAS_STATUS_RESERVED       1
>>> +
>>>    struct f2fs_gc_range {
>>>        __u32 sync;
>>>        __u64 start;
>>