For zoned devices, f2fs forbids direct IO and forces buffered IO
to serialize write IOs. However, the constraint does not apply to
read IOs.

Signed-off-by: Eunhee Rho <eunhee83.rho@samsung.com>
---
 fs/f2fs/f2fs.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index d0f428aef34b..f69731f17402 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4471,7 +4471,7 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
 	 * for blkzoned device, fallback direct IO to buffered IO, so
 	 * all IOs can be serialized by log-structured write.
 	 */
-	if (f2fs_sb_has_blkzoned(sbi))
+	if (f2fs_sb_has_blkzoned(sbi) && (rw == WRITE))
 		return true;
 	if (f2fs_lfs_mode(sbi) && (rw == WRITE)) {
 		if (block_unaligned_IO(inode, iocb, iter))
-- 
2.25.1

On 07/29, Eunhee Rho wrote:
> For zoned devices, f2fs forbids direct IO and forces buffered IO
> to serialize write IOs. However, the constraint does not apply to
> read IOs.
> 
> Signed-off-by: Eunhee Rho <eunhee83.rho@samsung.com>
> ---
>  fs/f2fs/f2fs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index d0f428aef34b..f69731f17402 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -4471,7 +4471,7 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
>  	 * for blkzoned device, fallback direct IO to buffered IO, so
>  	 * all IOs can be serialized by log-structured write.
>  	 */
> -	if (f2fs_sb_has_blkzoned(sbi))
> +	if (f2fs_sb_has_blkzoned(sbi) && (rw == WRITE))
>  		return true;

Actually we don't need to check the device type, but rely on the
filesystem allocation policy like the below lfs mode. Can we remove this
line simply?

>  	if (f2fs_lfs_mode(sbi) && (rw == WRITE)) {
>  		if (block_unaligned_IO(inode, iocb, iter))
> -- 
> 2.25.1

>On 07/29, Eunhee Rho wrote:
>> For zoned devices, f2fs forbids direct IO and forces buffered IO
>> to serialize write IOs. However, the constraint does not apply to
>> read IOs.
>> 
>> Signed-off-by: Eunhee Rho <eunhee83.rho@samsung.com>
>> ---
>>  fs/f2fs/f2fs.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index d0f428aef34b..f69731f17402 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -4471,7 +4471,7 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
>>  	 * for blkzoned device, fallback direct IO to buffered IO, so
>>  	 * all IOs can be serialized by log-structured write.
>>  	 */
>> -	if (f2fs_sb_has_blkzoned(sbi))
>> +	if (f2fs_sb_has_blkzoned(sbi) && (rw == WRITE))
>>  		return true;
>
>Actually we don't need to check the device type, but rely on the
>filesystem allocation policy like the below lfs mode. Can we remove this
>line simply?
>
>>  	if (f2fs_lfs_mode(sbi) && (rw == WRITE)) {
>>  		if (block_unaligned_IO(inode, iocb, iter))
>> -- 
>> 2.25.1
>

Yes, I will reflect on the next patch.
Thanks.

To ensure serialized IOs, f2fs allows only LFS mode for zoned
device. Remove redundant check for direct IO.

Signed-off-by: Eunhee Rho <eunhee83.rho@samsung.com>
---
 fs/f2fs/f2fs.h | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index ecd870e5d6da..ca9354746eec 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -4496,12 +4496,7 @@ static inline bool f2fs_force_buffered_io(struct inode *inode,
 	/* disallow direct IO if any of devices has unaligned blksize */
 	if (f2fs_is_multi_device(sbi) && !sbi->aligned_blksize)
 		return true;
-	/*
-	 * for blkzoned device, fallback direct IO to buffered IO, so
-	 * all IOs can be serialized by log-structured write.
-	 */
-	if (f2fs_sb_has_blkzoned(sbi))
-		return true;
+
 	if (f2fs_lfs_mode(sbi) && (rw == WRITE)) {
 		if (block_unaligned_IO(inode, iocb, iter))
 			return true;
-- 
2.25.1

On Fri, Jul 29, 2022 at 09:25:17AM +0900, Eunhee Rho wrote:
> For zoned devices, f2fs forbids direct IO and forces buffered IO
> to serialize write IOs. However, the constraint does not apply to
> read IOs.

Asymetric capabilitis will cause a whole lot of problems for us.  Can
we figure out why direct writes to zoned devices are not supported and
just fix that instead?