Re: [PATCH] fat: issue flush after the writeback of FAT

[OGAWA Hirofumi]

Hou Tao  writes:

> fsync() needs to make sure the data & meta-data of file are persistent
> after the return of fsync(), even when a power-failure occurs later.
> In the case of fat-fs, the FAT belongs to the meta-data of file,
> so we need to issue a flush after the writeback of FAT instead before.
>
> Also bail out early when any stage of fsync fails.
>
> Signed-off-by: Hou Tao 

Looks good.

Acked-by: OGAWA Hirofumi 

> ---
>  fs/fat/file.c | 11 ---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index b3bed32946b1..0e3ed79fcc3f 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -193,12 +193,17 @@ static int fat_file_release(struct inode *inode, struct 
> file *filp)
>  int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
>  {
>   struct inode *inode = filp->f_mapping->host;
> - int res, err;
> + int err;
> +
> + err = __generic_file_fsync(filp, start, end, datasync);
> + if (err)
> + return err;
>  
> - res = generic_file_fsync(filp, start, end, datasync);
>   err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
> + if (err)
> + return err;
>  
> - return res ? res : err;
> + return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
>  }

-- 
OGAWA Hirofumi 

Re: [PATCH] fat: issue flush after the writeback of FAT

[OGAWA Hirofumi]

"Darrick J. Wong"  writes:

>> +err = __generic_file_fsync(filp, start, end, datasync);
>> +if (err)
>> +return err;
>>  
>> -res = generic_file_fsync(filp, start, end, datasync);
>>  err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
>
> Huh.  I would've thought that flushing the FAT would also be required
> at the end of a WB_SYNC_ALL (aka data integrity) writepages call?

In fatfs implement, FAT area is flushed by sync_mapping_buffers(fat_inode). 
(FAT buffer is dirtied only by using bh->b_assoc_map to fat_inode)

Thanks.
-- 
OGAWA Hirofumi 

Re: [PATCH] fat: issue flush after the writeback of FAT

[Darrick J. Wong]

On Tue, Apr 09, 2019 at 11:01:58AM +0800, Hou Tao wrote:
> fsync() needs to make sure the data & meta-data of file are persistent
> after the return of fsync(), even when a power-failure occurs later.
> In the case of fat-fs, the FAT belongs to the meta-data of file,
> so we need to issue a flush after the writeback of FAT instead before.
> 
> Also bail out early when any stage of fsync fails.
> 
> Signed-off-by: Hou Tao 
> ---
>  fs/fat/file.c | 11 ---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index b3bed32946b1..0e3ed79fcc3f 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -193,12 +193,17 @@ static int fat_file_release(struct inode *inode, struct 
> file *filp)
>  int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
>  {
>   struct inode *inode = filp->f_mapping->host;
> - int res, err;
> + int err;
> +
> + err = __generic_file_fsync(filp, start, end, datasync);
> + if (err)
> + return err;
>  
> - res = generic_file_fsync(filp, start, end, datasync);
>   err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);

Huh.  I would've thought that flushing the FAT would also be required
at the end of a WB_SYNC_ALL (aka data integrity) writepages call?

The patch itself seems good, though.

--D

> + if (err)
> + return err;
>  
> - return res ? res : err;
> + return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
>  }
>  
>  
> -- 
> 2.16.2.dirty
> 

[PATCH] fat: issue flush after the writeback of FAT

[Hou Tao]

fsync() needs to make sure the data & meta-data of file are persistent
after the return of fsync(), even when a power-failure occurs later.
In the case of fat-fs, the FAT belongs to the meta-data of file,
so we need to issue a flush after the writeback of FAT instead before.

Also bail out early when any stage of fsync fails.

Signed-off-by: Hou Tao 
---
 fs/fat/file.c | 11 ---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/fat/file.c b/fs/fat/file.c
index b3bed32946b1..0e3ed79fcc3f 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -193,12 +193,17 @@ static int fat_file_release(struct inode *inode, struct 
file *filp)
 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 {
struct inode *inode = filp->f_mapping->host;
-   int res, err;
+   int err;
+
+   err = __generic_file_fsync(filp, start, end, datasync);
+   if (err)
+   return err;
 
-   res = generic_file_fsync(filp, start, end, datasync);
err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
+   if (err)
+   return err;
 
-   return res ? res : err;
+   return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 }
 
 
-- 
2.16.2.dirty