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SubjectRe: [f2fs-dev] [PATCH 2/6] f2fs: do not expose unwritten blocks to user by DIO
On 11/17, Chao Yu wrote:
> 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);
>
> We will leave FADVISE_TRUNC_BIT flag in below call path, is this as expected?
>
> - fallocate
> - expand_inode_data
> - f2fs_map_blocks(F2FS_GET_BLOCK_PRE_DIO)

I missed it. :)

--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1698,6 +1698,7 @@ static int expand_inode_data(struct inode *inode, loff_t offset,

map.m_seg_type = CURSEG_COLD_DATA_PINNED;
err = f2fs_map_blocks(inode, &map, 1, F2FS_GET_BLOCK_PRE_DIO);
+ file_dont_truncate(inode);

up_write(&sbi->pin_sem);

> Thanks,
>
> > 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);
> > }
> > +
> > clear_inode_flag(inode, FI_PREALLOCATED_ALL);
> > if (ret > 0)
> >

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