Re: [f2fs-dev] [PATCH v3] f2fs: prevent writing without fallocate() for pinned files

[Daeho Jeong]

On Fri, Mar 22, 2024 at 9:26 PM Chao Yu <chao@xxxxxxxxxx> wrote:
>
> On 2024/3/21 1:42, Daeho Jeong wrote:
> > On Wed, Mar 20, 2024 at 2:38 AM Chao Yu <chao@xxxxxxxxxx> wrote:
> >>
> >> On 2024/3/20 5:23, Daeho Jeong wrote:
> >>> From: Daeho Jeong <daehojeong@xxxxxxxxxx>
> >>>
> >>> In a case writing without fallocate(), we can't guarantee it's allocated
> >>> in the conventional area for zoned stroage.
> >>>
> >>> Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>
> >>> ---
> >>> v2: covered the direct io case
> >>> v3: covered the mkwrite case
> >>> ---
> >>>    fs/f2fs/data.c | 14 ++++++++++++--
> >>>    fs/f2fs/file.c | 16 ++++++++--------
> >>>    2 files changed, 20 insertions(+), 10 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> >>> index c21b92f18463..d3e5ab2736a6 100644
> >>> --- a/fs/f2fs/data.c
> >>> +++ b/fs/f2fs/data.c
> >>> @@ -1584,8 +1584,11 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, int flag)
> >>>
> >>>        /* use out-place-update for direct IO under LFS mode */
> >>>        if (map->m_may_create &&
> >>> -         (is_hole || (f2fs_lfs_mode(sbi) && flag == F2FS_GET_BLOCK_DIO))) {
> >>> -             if (unlikely(f2fs_cp_error(sbi))) {
> >>> +         (is_hole || (f2fs_lfs_mode(sbi) && flag == F2FS_GET_BLOCK_DIO &&
> >>> +                      !f2fs_is_pinned_file(inode)))) {
> >>> +             if (unlikely(f2fs_cp_error(sbi)) ||
> >>> +                 (f2fs_is_pinned_file(inode) && is_hole &&
> >>> +                  flag != F2FS_GET_BLOCK_PRE_DIO)) {
> >>>                        err = -EIO;
> >>>                        goto sync_out;
> >>>                }
> >>> @@ -3378,6 +3381,8 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
> >>>                f2fs_map_lock(sbi, flag);
> >>>                locked = true;
> >>>        } else if ((pos & PAGE_MASK) >= i_size_read(inode)) {
> >>> +             if (f2fs_is_pinned_file(inode))
> >>> +                     return -EIO;
> >>>                f2fs_map_lock(sbi, flag);
> >>>                locked = true;
> >>>        }
> >>> @@ -3407,6 +3412,11 @@ static int prepare_write_begin(struct f2fs_sb_info *sbi,
> >>>
> >>>        if (!f2fs_lookup_read_extent_cache_block(inode, index,
> >>>                                                 &dn.data_blkaddr)) {
> >>> +             if (f2fs_is_pinned_file(inode)) {
> >>> +                     err = -EIO;
> >>> +                     goto out;
> >>> +             }
> >>> +
> >>>                if (locked) {
> >>>                        err = f2fs_reserve_block(&dn, index);
> >>>                        goto out;
> >>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >>> index 82277e95c88f..4db3b21c804b 100644
> >>> --- a/fs/f2fs/file.c
> >>> +++ b/fs/f2fs/file.c
> >>> @@ -57,7 +57,7 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> >>>        struct inode *inode = file_inode(vmf->vma->vm_file);
> >>>        struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>>        struct dnode_of_data dn;
> >>> -     bool need_alloc = true;
> >>> +     bool need_alloc = !f2fs_is_pinned_file(inode);
> >>
> >> Will this check races w/ pinfile get|set?
> >
> > Do you mean "set/clear" case? I believe "set" case is okay, since we
>
> Yup,
>
> > can't set if the inode already has a data block. For "clear" case, I
>
> However, we can set pinfile on written inode in regular block device:

You're right. I missed it. Maybe I think we should keep the concept
consistent across devices regardless of zoned storage support. How
about preventing file pinning for already written inodes across all
device types? I am changing the pinfile concept by allowing the users
to write on only fallocate()-ed space.

>
>         if (f2fs_sb_has_blkzoned(sbi) && F2FS_HAS_BLOCKS(inode)) {
>                 ret = -EFBIG;
>                 goto out;
>         }
>
> Should we add the logic only if blkzoned feture is enabled?
>
> > believe mkwrite failure is okay in racy conditions caused by clearing
> > the pin flag. What do you think?
>
> Or we can use filemap_invalidate_lock() in f2fs_ioc_set_pin_file() to
> avoid the race condition?
>
> Thanks,
>
> >
> >>
> >> Thanks,
> >>
> >>>        int err = 0;
> >>>        vm_fault_t ret;
> >>>
> >>> @@ -114,19 +114,15 @@ static vm_fault_t f2fs_vm_page_mkwrite(struct vm_fault *vmf)
> >>>                goto out_sem;
> >>>        }
> >>>
> >>> +     set_new_dnode(&dn, inode, NULL, NULL, 0);
> >>>        if (need_alloc) {
> >>>                /* block allocation */
> >>> -             set_new_dnode(&dn, inode, NULL, NULL, 0);
> >>>                err = f2fs_get_block_locked(&dn, page->index);
> >>> -     }
> >>> -
> >>> -#ifdef CONFIG_F2FS_FS_COMPRESSION
> >>> -     if (!need_alloc) {
> >>> -             set_new_dnode(&dn, inode, NULL, NULL, 0);
> >>> +     } else {
> >>>                err = f2fs_get_dnode_of_data(&dn, page->index, LOOKUP_NODE);
> >>>                f2fs_put_dnode(&dn);
> >>>        }
> >>> -#endif
> >>> +
> >>>        if (err) {
> >>>                unlock_page(page);
> >>>                goto out_sem;
> >>> @@ -4611,6 +4607,10 @@ static int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *iter,
> >>>                        return ret;
> >>>        }
> >>>
> >>> +     /* For pinned files, it should be fallocate()-ed in advance. */
> >>> +     if (f2fs_is_pinned_file(inode))
> >>> +             return 0;
> >>> +
> >>>        /* Do not preallocate blocks that will be written partially in 4KB. */
> >>>        map.m_lblk = F2FS_BLK_ALIGN(pos);
> >>>        map.m_len = F2FS_BYTES_TO_BLK(pos + count);