Messages in this thread | | | Date | Thu, 2 Dec 2021 10:39:20 +0800 | Subject | Re: [f2fs-dev] [PATCH 2/6] f2fs: do not expose unwritten blocks to user by DIO | From | Chao Yu <> |
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On 2021/11/17 5:45, Jaegeuk Kim wrote: > DIO preallocates physical blocks before writing data, but if an error occurrs > or power-cut happens, we can see block contents from the disk. This patch tries > to fix it by 1) turning to buffered writes for DIO into holes, 2) truncating > unwritten blocks from error or power-cut. > > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > fs/f2fs/data.c | 5 ++++- > fs/f2fs/f2fs.h | 5 +++++ > fs/f2fs/file.c | 24 +++++++++++++++++++++++- > 3 files changed, 32 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c > index 3b27fb7daa8b..7ac1a39fcad2 100644 > --- a/fs/f2fs/data.c > +++ b/fs/f2fs/data.c > @@ -1543,8 +1543,11 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map, > flag != F2FS_GET_BLOCK_DIO); > err = __allocate_data_block(&dn, > map->m_seg_type); > - if (!err) > + if (!err) { > + if (flag == F2FS_GET_BLOCK_PRE_DIO) > + file_need_truncate(inode); > set_inode_flag(inode, FI_APPEND_WRITE); > + } > } > if (err) > goto sync_out; > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index be871a79c634..14bea669f87e 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -654,6 +654,7 @@ enum { > #define FADVISE_KEEP_SIZE_BIT 0x10 > #define FADVISE_HOT_BIT 0x20 > #define FADVISE_VERITY_BIT 0x40 > +#define FADVISE_TRUNC_BIT 0x80 > > #define FADVISE_MODIFIABLE_BITS (FADVISE_COLD_BIT | FADVISE_HOT_BIT) > > @@ -681,6 +682,10 @@ enum { > #define file_is_verity(inode) is_file(inode, FADVISE_VERITY_BIT) > #define file_set_verity(inode) set_file(inode, FADVISE_VERITY_BIT) > > +#define file_should_truncate(inode) is_file(inode, FADVISE_TRUNC_BIT) > +#define file_need_truncate(inode) set_file(inode, FADVISE_TRUNC_BIT) > +#define file_dont_truncate(inode) clear_file(inode, FADVISE_TRUNC_BIT) > + > #define DEF_DIR_LEVEL 0 > > enum { > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 4bf77a5bf998..ec8de0662437 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -960,10 +960,21 @@ int f2fs_setattr(struct user_namespace *mnt_userns, struct dentry *dentry, > down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > filemap_invalidate_lock(inode->i_mapping); > > + /* > + * Truncate stale preallocated blocks used by the previous DIO. > + */ > + if (file_should_truncate(inode)) { > + err = f2fs_truncate(inode); > + if (err) > + goto out_unlock; > + file_dont_truncate(inode); > + } > + > truncate_setsize(inode, attr->ia_size); > > if (attr->ia_size <= old_size) > err = f2fs_truncate(inode); > +out_unlock: > /* > * do not trim all blocks after i_size if target size is > * larger than i_size. > @@ -4257,6 +4268,13 @@ static int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *iter) > /* If it will be an out-of-place direct write, don't bother. */ > if (dio && f2fs_lfs_mode(sbi)) > return 0; > + /* > + * Don't preallocate holes aligned to DIO_SKIP_HOLES which turns into > + * buffered IO, if DIO meets any holes. > + */ > + if (dio && i_size_read(inode) && > + (F2FS_BYTES_TO_BLK(pos) < F2FS_BLK_ALIGN(i_size_read(inode)))) > + return 0; > > /* No-wait I/O can't allocate blocks. */ > if (iocb->ki_flags & IOCB_NOWAIT) > @@ -4366,10 +4384,14 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from) > if (preallocated > 0 && i_size_read(inode) < target_size) { > down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > filemap_invalidate_lock(inode->i_mapping); > - f2fs_truncate(inode); > + if (!f2fs_truncate(inode)) > + file_dont_truncate(inode); > filemap_invalidate_unlock(inode->i_mapping); > up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]); > + } else { > + file_dont_truncate(inode);
How about this case:
- touch file - DIO write [0, 8kb] to file - preallocate 2 physical blocks - set FADVISE_TRUNC_BIT - SPO - BUFIO write [0, 4kb] to file - file_dont_truncate -- it leaks unwritten [4kb, 8kb] to user after truncating file to 8kb
Thanks,
> } > + > clear_inode_flag(inode, FI_PREALLOCATED_ALL); > > if (ret > 0) >
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