Re: [PATCH] f2fs: compress: don't force buffered io when in COMPR_MODE_USER mode

[Yangtao Li]

On 2023/6/19 8:54, Chao Yu wrote:

> On 2023/6/13 12:14, Yangtao Li wrote:
> > On 2023/6/12 22:38, Chao Yu wrote:
> > > On 2023/6/9 21:15, Yangtao Li wrote:
> > > > It is observed that when in user compression mode
> > > > (compress_extension=*),
> > > > even though the file is not compressed, the file is still forced to 
> > > > use
> > > > buffer io, which makes the AndroBench sequential read and write drop
> > > > significantly. In fact, when the file is not compressed, we don't need
> > > > to force it to buffer io.
> > > >
> > > >                    | w/o patch | w/ patch |
> > > > seq read  (MB/s) | 1320.068  | 3696.154 |
> > > > seq write (MB/s) | 617.996   | 2978.478 |
> > > >
> > > > Fixes: 4c8ff7095bef ("f2fs: support data compression")
> > > > Signed-off-by: Qi Han <hanqi@xxxxxxxx>
> > > > Signed-off-by: Yangtao Li <frank.li@xxxxxxxx>
> > > > ---
> > > >    fs/f2fs/f2fs.h | 14 ++++++++++++++
> > > >    fs/f2fs/file.c |  2 +-
> > > >    2 files changed, 15 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > > > index 1efcfd9e5a99..7f5472525310 100644
> > > > --- a/fs/f2fs/f2fs.h
> > > > +++ b/fs/f2fs/f2fs.h
> > > > @@ -3168,6 +3168,20 @@ static inline int f2fs_compressed_file(struct
> > > > inode *inode)
> > > >            is_inode_flag_set(inode, FI_COMPRESSED_FILE);
> > > >    }
> > > >    +static inline bool f2fs_is_compressed_file(struct inode *inode)
> > > > +{
> > > > +    int compress_mode = F2FS_OPTION(F2FS_I_SB(inode)).compress_mode;
> > > > +
> > > > +    if (compress_mode == COMPR_MODE_FS)
> > > > +        return f2fs_compressed_file(inode);
> > > > +    else if (atomic_read(&F2FS_I(inode)->i_compr_blocks) ||
> > >
> > > Should check dirty page as well? i_compr_blocks may increase after
> > > data writeback.
> > IIUC, in COMPR_MODE_USER mode, i_compr_blocks will only be updated when
> > FI_ENABLE_COMPRESS is enabled.
> >
> > If FI_ENABLE_COMPRESS is not enabled, i_compr_blocks will never be
> > updated after data writeback.
> >
> > So there is no need to additionally judge whether there is a dirty page?
>
> Oh, user mode, that's correct.
>
> If we allow dio/aio on compress file, it needs to consider race case in
> between aio and ioc_compress_file.


The inode_lock is already held in f2fs_file_write_iter and 
f2fs_ioc_compress_file, I guess this is enough?

What else?


4691 static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct 
iov_iter *from)
4692 {
4693         struct inode *inode = file_inode(iocb->ki_filp);
4694         const loff_t orig_pos = iocb->ki_pos;
4695         const size_t orig_count = iov_iter_count(from);
4696         loff_t target_size;
4697         bool dio;
4698         bool may_need_sync = true;
4699         int preallocated;
4700         ssize_t ret;
4701
4702         if (unlikely(f2fs_cp_error(F2FS_I_SB(inode)))) {
4703                 ret = -EIO;
4704                 goto out;
4705         }
4706
4707         if (!f2fs_is_compress_backend_ready(inode)) {
4708                 ret = -EOPNOTSUPP;
4709                 goto out;
4710         }
4711
4712         if (iocb->ki_flags & IOCB_NOWAIT) {
4713                 if (!inode_trylock(inode)) {
4714                         ret = -EAGAIN;
4715                         goto out;
4716                 }
4717         } else {
4718                 inode_lock(inode);
4719         }


4115 static int f2fs_ioc_compress_file(struct file *filp)
4116 {
4117         struct inode *inode = file_inode(filp);
4118         struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
4119         pgoff_t page_idx = 0, last_idx;
4120         unsigned int blk_per_seg = sbi->blocks_per_seg;
4121         int cluster_size = F2FS_I(inode)->i_cluster_size;
4122         int count, ret;
4123
4124         if (!f2fs_sb_has_compression(sbi) ||
4125                         F2FS_OPTION(sbi).compress_mode != 
COMPR_MODE_USER)
4126                 return -EOPNOTSUPP;
4127
4128         if (!(filp->f_mode & FMODE_WRITE))
4129                 return -EBADF;
4130
4131         if (!f2fs_compressed_file(inode))
4132                 return -EINVAL;
4133
4134         f2fs_balance_fs(sbi, true);
4135
4136         file_start_write(filp);
4137         inode_lock(inode);


Thanks,

> Thanks,
>
> > Thanks,
> >
> > > Thanks,
> > >
> > > > +        is_inode_flag_set(inode, FI_COMPRESS_RELEASED) ||
> > > > +        is_inode_flag_set(inode, FI_ENABLE_COMPRESS))
> > > > +        return true;
> > > > +
> > > > +    return false;
> > > > +}
> > > > +
> > > >    static inline bool f2fs_need_compress_data(struct inode *inode)
> > > >    {
> > > >        int compress_mode = 
> > > > F2FS_OPTION(F2FS_I_SB(inode)).compress_mode;
> > > > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > > > index 74ecc9e20619..0698129b2165 100644
> > > > --- a/fs/f2fs/file.c
> > > > +++ b/fs/f2fs/file.c
> > > > @@ -821,7 +821,7 @@ static bool f2fs_force_buffered_io(struct inode
> > > > *inode, int rw)
> > > >            return true;
> > > >        if (fsverity_active(inode))
> > > >            return true;
> > > > -    if (f2fs_compressed_file(inode))
> > > > +    if (f2fs_is_compressed_file(inode))
> > > >            return true;
> > > >          /* disallow direct IO if any of devices has unaligned 
> > > > blksize */