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

From: Daeho Jeong
Date: Wed Mar 20 2024 - 13:42:20 EST


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
can't set if the inode already has a data block. For "clear" case, I
believe mkwrite failure is okay in racy conditions caused by clearing
the pin flag. What do you think?

>
> 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);