Re: [f2fs-dev] [PATCH v2] f2fs: introduce F2FS_IOC_START_ATOMIC_REPLACE

[Chao Yu <chao@kernel.org>]

On 2022/9/30 7:33, Daeho Jeong wrote:
> On Thu, Sep 29, 2022 at 3:54 PM Chao Yu <chao@kernel.org> wrote:
>>
>> On 2022/9/30 0:13, Daeho Jeong wrote:
>>> On Thu, Sep 29, 2022 at 12:36 AM Chao Yu <chao@kernel.org> wrote:
>>>>
>>>> On 2022/9/20 9:40, Daeho Jeong wrote:
>>>>> From: Daeho Jeong <daehojeong@google.com>
>>>>>
>>>>> introduce a new ioctl to replace the whole content of a file atomically,
>>>>> which means it induces truncate and content update at the same time.
>>>>> We can start it with F2FS_IOC_START_ATOMIC_REPLACE and complete it with
>>>>> F2FS_IOC_COMMIT_ATOMIC_WRITE. Or abort it with
>>>>> F2FS_IOC_ABORT_ATOMIC_WRITE.
>>>>>
>>>>> Signed-off-by: Daeho Jeong <daehojeong@google.com>
>>>>> ---
>>>>> v2: add undefined ioctl number reported by <lkp@intel.com>
>>>>> ---
>>>>>     fs/f2fs/data.c            |  3 +++
>>>>>     fs/f2fs/f2fs.h            |  1 +
>>>>>     fs/f2fs/file.c            | 12 ++++++++++--
>>>>>     fs/f2fs/segment.c         | 14 +++++++++++++-
>>>>>     include/uapi/linux/f2fs.h |  1 +
>>>>>     5 files changed, 28 insertions(+), 3 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>>> index 6cd29a575105..d3d32db3a25d 100644
>>>>> --- a/fs/f2fs/data.c
>>>>> +++ b/fs/f2fs/data.c
>>>>> @@ -3438,6 +3438,9 @@ static int prepare_atomic_write_begin(struct f2fs_sb_info *sbi,
>>>>>         else if (*blk_addr != NULL_ADDR)
>>>>>                 return 0;
>>>>>
>>>>> +     if (is_inode_flag_set(inode, FI_ATOMIC_REPLACE))
>>>>> +             goto reserve_block;
>>>>> +
>>>>>         /* Look for the block in the original inode */
>>>>>         err = __find_data_block(inode, index, &ori_blk_addr);
>>>>>         if (err)
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index 539da7f12cfc..2c49da12d6d8 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -764,6 +764,7 @@ enum {
>>>>>         FI_COMPRESS_RELEASED,   /* compressed blocks were released */
>>>>>         FI_ALIGNED_WRITE,       /* enable aligned write */
>>>>>         FI_COW_FILE,            /* indicate COW file */
>>>>> +     FI_ATOMIC_REPLACE,      /* indicate atomic replace */
>>>>>         FI_MAX,                 /* max flag, never be used */
>>>>>     };
>>>>>
>>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>>> index 4f9b80c41b1e..4abd9d2a55b3 100644
>>>>> --- a/fs/f2fs/file.c
>>>>> +++ b/fs/f2fs/file.c
>>>>> @@ -1982,7 +1982,7 @@ static int f2fs_ioc_getversion(struct file *filp, unsigned long arg)
>>>>>         return put_user(inode->i_generation, (int __user *)arg);
>>>>>     }
>>>>>
>>>>> -static int f2fs_ioc_start_atomic_write(struct file *filp)
>>>>> +static int f2fs_ioc_start_atomic_write(struct file *filp, bool truncate)
>>>>>     {
>>>>>         struct inode *inode = file_inode(filp);
>>>>>         struct user_namespace *mnt_userns = file_mnt_user_ns(filp);
>>>>> @@ -2051,6 +2051,12 @@ static int f2fs_ioc_start_atomic_write(struct file *filp)
>>>>>
>>>>>         isize = i_size_read(inode);
>>>>>         fi->original_i_size = isize;
>>>>> +     if (truncate) {
>>>>> +             set_inode_flag(inode, FI_ATOMIC_REPLACE);
>>>>> +             truncate_inode_pages_final(inode->i_mapping);
>>>>> +             f2fs_i_size_write(inode, 0);
>>>>> +             isize = 0;
>>>>> +     }
>>>>
>>>> Hi Daeho,
>>>>
>>>> isize should be updated after tagging inode as atomic_write one?
>>>> otherwise f2fs_mark_inode_dirty_sync() may update isize to inode page,
>>>> latter checkpoint may persist that change? IIUC...
>>>>
>>>> Thanks,
>>>
>>> Hi Chao,
>>>
>>> The first patch of this patchset prevents the inode page from being
>>> updated as dirty for atomic file cases.
>>> Is there any other chances for the inode page to be marked as dirty?
>>
>> I mean:
>>
>> Thread A                                Thread B
>> - f2fs_ioc_start_atomic_write
>>    - f2fs_i_size_write(inode, 0)
>>     - f2fs_mark_inode_dirty_sync
>>                                          - checkpoint
>>                                           - persist inode with incorrect zero isize
>>
>>    - set_inode_flag(inode, FI_ATOMIC_FILE)
>>
>> Am I missing something?
>>
> 
> So, f2fs_mark_inode_dirty_sync() will not work for atomic files
> anymore, which means it doesn't make the inode dirty.
> Plz, refer to the first patch of this patchset. Or I might be confused
> with something. :(

I mean FI_ATOMIC_FILE was set after f2fs_i_size_write(), so inode will be set
as dirty.

Thanks,

> 
> @@ -30,6 +30,9 @@ void f2fs_mark_inode_dirty_sync(struct inode *inode,
> bool sync)
>          if (f2fs_inode_dirtied(inode, sync))
>                  return;
> 
> +       if (f2fs_is_atomic_file(inode))
> +               return;
> +
>          mark_inode_dirty_sync(inode);
>   }
> 
> 
> 
> 
> 
>> Thanks,
>>
>>>
>>> Thanks,
>>>
>>>>
>>>>>         f2fs_i_size_write(fi->cow_inode, isize);
>>>>>
>>>>>         spin_lock(&sbi->inode_lock[ATOMIC_FILE]);
>>>>> @@ -4080,7 +4086,9 @@ static long __f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
>>>>>         case FS_IOC_GETVERSION:
>>>>>                 return f2fs_ioc_getversion(filp, arg);
>>>>>         case F2FS_IOC_START_ATOMIC_WRITE:
>>>>> -             return f2fs_ioc_start_atomic_write(filp);
>>>>> +             return f2fs_ioc_start_atomic_write(filp, false);
>>>>> +     case F2FS_IOC_START_ATOMIC_REPLACE:
>>>>> +             return f2fs_ioc_start_atomic_write(filp, true);
>>>>>         case F2FS_IOC_COMMIT_ATOMIC_WRITE:
>>>>>                 return f2fs_ioc_commit_atomic_write(filp);
>>>>>         case F2FS_IOC_ABORT_ATOMIC_WRITE:
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 143b7ea0fb8e..c524538a9013 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -263,14 +263,26 @@ static void __complete_revoke_list(struct inode *inode, struct list_head *head,
>>>>>                                         bool revoke)
>>>>>     {
>>>>>         struct revoke_entry *cur, *tmp;
>>>>> +     pgoff_t start_index = 0;
>>>>> +     bool truncate = is_inode_flag_set(inode, FI_ATOMIC_REPLACE);
>>>>>
>>>>>         list_for_each_entry_safe(cur, tmp, head, list) {
>>>>> -             if (revoke)
>>>>> +             if (revoke) {
>>>>>                         __replace_atomic_write_block(inode, cur->index,
>>>>>                                                 cur->old_addr, NULL, true);
>>>>> +             } else if (truncate) {
>>>>> +                     f2fs_truncate_hole(inode, start_index, cur->index);
>>>>> +                     start_index = cur->index + 1;
>>>>> +             }
>>>>> +
>>>>>                 list_del(&cur->list);
>>>>>                 kmem_cache_free(revoke_entry_slab, cur);
>>>>>         }
>>>>> +
>>>>> +     if (!revoke && truncate) {
>>>>> +             f2fs_do_truncate_blocks(inode, start_index * PAGE_SIZE, false);
>>>>> +             clear_inode_flag(inode, FI_ATOMIC_REPLACE);
>>>>> +     }
>>>>>     }
>>>>>
>>>>>     static int __f2fs_commit_atomic_write(struct inode *inode)
>>>>> diff --git a/include/uapi/linux/f2fs.h b/include/uapi/linux/f2fs.h
>>>>> index 3121d127d5aa..955d440be104 100644
>>>>> --- a/include/uapi/linux/f2fs.h
>>>>> +++ b/include/uapi/linux/f2fs.h
>>>>> @@ -42,6 +42,7 @@
>>>>>                                                 struct f2fs_comp_option)
>>>>>     #define F2FS_IOC_DECOMPRESS_FILE    _IO(F2FS_IOCTL_MAGIC, 23)
>>>>>     #define F2FS_IOC_COMPRESS_FILE              _IO(F2FS_IOCTL_MAGIC, 24)
>>>>> +#define F2FS_IOC_START_ATOMIC_REPLACE        _IO(F2FS_IOCTL_MAGIC, 25)
>>>>>
>>>>>     /*
>>>>>      * should be same as XFS_IOC_GOINGDOWN.