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SubjectRe: [PATCH] f2fs: Fix direct IO handling
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On 2019/11/27 7:44, Jaegeuk Kim wrote:
> On 11/26, Damien Le Moal wrote:
>> f2fs_preallocate_blocks() identifies direct IOs using the IOCB_DIRECT
>> flag for a kiocb structure. However, the file system direct IO handler
>> function f2fs_direct_IO() may have decided that a direct IO has to be
>> exececuted as a buffered IO using the function f2fs_force_buffered_io().
>> This is the case for instance for volumes including zoned block device
>> and for unaligned write IOs with LFS mode enabled.
>>
>> These 2 different methods of identifying direct IOs can result in
>> inconsistencies generating stale data access for direct reads after a
>> direct IO write that is treated as a buffered write. Fix this
>> inconsistency by combining the IOCB_DIRECT flag test with the result
>> of f2fs_force_buffered_io().
>>
>> Reported-by: Javier Gonzalez <javier@javigon.com>
>> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
>> ---
>> fs/f2fs/data.c | 4 +++-
>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>> index 5755e897a5f0..8ac2d3b70022 100644
>> --- a/fs/f2fs/data.c
>> +++ b/fs/f2fs/data.c
>> @@ -1073,6 +1073,8 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>> int flag;
>> int err = 0;
>> bool direct_io = iocb->ki_flags & IOCB_DIRECT;
>> + bool do_direct_io = direct_io &&
>> + !f2fs_force_buffered_io(inode, iocb, from);
>>
>> /* convert inline data for Direct I/O*/
>> if (direct_io) {
>> @@ -1081,7 +1083,7 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
>> return err;
>> }
>>
>> - if (direct_io && allow_outplace_dio(inode, iocb, from))
>> + if (do_direct_io && allow_outplace_dio(inode, iocb, from))
>
> It seems f2fs_force_buffered_io() includes allow_outplace_dio().
>
> How about this?
> ---
> fs/f2fs/data.c | 13 -------------
> fs/f2fs/file.c | 35 +++++++++++++++++++++++++----------
> 2 files changed, 25 insertions(+), 23 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index a034cd0ce021..fc40a72f7827 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1180,19 +1180,6 @@ int f2fs_preallocate_blocks(struct kiocb *iocb, struct iov_iter *from)
> int err = 0;
> bool direct_io = iocb->ki_flags & IOCB_DIRECT;
>
> - /* convert inline data for Direct I/O*/
> - if (direct_io) {
> - err = f2fs_convert_inline_inode(inode);
> - if (err)
> - return err;
> - }
> -
> - if (direct_io && allow_outplace_dio(inode, iocb, from))
> - return 0;
> -
> - if (is_inode_flag_set(inode, FI_NO_PREALLOC))
> - return 0;
> -
> map.m_lblk = F2FS_BLK_ALIGN(iocb->ki_pos);
> map.m_len = F2FS_BYTES_TO_BLK(iocb->ki_pos + iov_iter_count(from));
> if (map.m_len > map.m_lblk)
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index c0560d62dbee..6b32ac6c3382 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -3386,18 +3386,33 @@ static ssize_t f2fs_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
> ret = -EAGAIN;
> goto out;
> }
> - } else {
> - preallocated = true;
> - target_size = iocb->ki_pos + iov_iter_count(from);
> + goto write;
> + }
>
> - err = f2fs_preallocate_blocks(iocb, from);
> - if (err) {
> - clear_inode_flag(inode, FI_NO_PREALLOC);
> - inode_unlock(inode);
> - ret = err;
> - goto out;
> - }
> + if (is_inode_flag_set(inode, FI_NO_PREALLOC))
> + goto write;
> +
> + if (iocb->ki_flags & IOCB_DIRECT) {
> + /* convert inline data for Direct I/O*/

Minor thing.

I/O */

> + err = f2fs_convert_inline_inode(inode);
> + if (err)
> + goto out_err;
> +
> + if (!f2fs_force_buffered_io(inode, iocb, from))
> + goto write;

We can call f2fs_convert_inline_inode() here to avoid unneeded inline
conversion.

Thanks,

> + }
> + preallocated = true;
> + target_size = iocb->ki_pos + iov_iter_count(from);
> +
> + err = f2fs_preallocate_blocks(iocb, from);
> + if (err) {
> +out_err:
> + clear_inode_flag(inode, FI_NO_PREALLOC);
> + inode_unlock(inode);
> + ret = err;
> + goto out;
> }
> +write:
> ret = __generic_file_write_iter(iocb, from);
> clear_inode_flag(inode, FI_NO_PREALLOC);
>
>

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