Re: [PATCH 09/11] fs: handle FIEMAP_FLAG_SYNC in fiemap_prep

[Ritesh Harjani <riteshh@xxxxxxxxxxxxx>]

On 4/27/20 11:49 PM, Christoph Hellwig wrote:
> By moving FIEMAP_FLAG_SYNC handling to fiemap_prep we ensure it is
> handled once instead of duplicated, but can still be done under fs locks,
> like xfs/iomap intended with its duplicate handling.  Also make sure the
> error value of filemap_write_and_wait is propagated to user space.


Forgot to remove filemap_write_and_wait() from
ext4_ioctl_get_es_cache() ?


> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
>   fs/btrfs/inode.c      |  4 +---
>   fs/cifs/smb2ops.c     |  3 +--
>   fs/ext4/extents.c     |  2 +-
>   fs/f2fs/data.c        |  3 +--
>   fs/ioctl.c            | 10 ++++++----
>   fs/iomap/fiemap.c     |  8 +-------
>   fs/nilfs2/inode.c     |  2 +-
>   fs/ocfs2/extent_map.c |  5 +----
>   fs/overlayfs/inode.c  |  4 ----
>   9 files changed, 13 insertions(+), 28 deletions(-)
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 1f1ec361089b3..529ffa5e7b452 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -8243,14 +8243,12 @@ static ssize_t btrfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
>   	return ret;
>   }
>   
> -#define BTRFS_FIEMAP_FLAGS	(FIEMAP_FLAG_SYNC)
> -
>   static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   		__u64 start, __u64 len)
>   {
>   	int	ret;
>   
> -	ret = fiemap_prep(inode, fieinfo, start, &len, BTRFS_FIEMAP_FLAGS);
> +	ret = fiemap_prep(inode, fieinfo, start, &len, 0);
>   	if (ret)
>   		return ret;
>   
> diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
> index 8a2e94931dc96..32880fca6d8d8 100644
> --- a/fs/cifs/smb2ops.c
> +++ b/fs/cifs/smb2ops.c
> @@ -3408,8 +3408,7 @@ static int smb3_fiemap(struct cifs_tcon *tcon,
>   	int i, num, rc, flags, last_blob;
>   	u64 next;
>   
> -	rc = fiemap_prep(cfile->dentry->d_inode, fei, start, &len,
> -			FIEMAP_FLAG_SYNC);
> +	rc = fiemap_prep(cfile->dentry->d_inode, fei, start, &len, 0);
>   	if (rc)
>   		rc;
>   
> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> index 41f73dea92cac..93574e88f6543 100644
> --- a/fs/ext4/extents.c
> +++ b/fs/ext4/extents.c
> @@ -4908,7 +4908,7 @@ int ext4_get_es_cache(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   		fieinfo->fi_flags &= ~FIEMAP_FLAG_CACHE;
>   	}
>   
> -	error = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_SYNC);
> +	error = fiemap_prep(inode, fieinfo, start, &len, 0);
>   	if (error)
>   		return error;
>   
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index 03faafc591b17..9de7dc476ed16 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -1825,8 +1825,7 @@ int f2fs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   			return ret;
>   	}
>   
> -	ret = fiemap_prep(inode, fieinfo, start, &len,
> -			FIEMAP_FLAG_SYNC | FIEMAP_FLAG_XATTR);
> +	ret = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_XATTR);
>   	if (ret)
>   		return ret;
>   
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 4d94c20c9596b..ae0d228d18a16 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -162,6 +162,7 @@ int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   {
>   	u64 maxbytes = inode->i_sb->s_maxbytes;
>   	u32 incompat_flags;
> +	int ret = 0;
>   
>   	if (*len == 0)
>   		return -EINVAL;
> @@ -174,13 +175,17 @@ int fiemap_prep(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   	if (*len > maxbytes || (maxbytes - *len) < start)
>   		*len = maxbytes - start;
>   
> +	supported_flags |= FIEMAP_FLAG_SYNC;
>   	supported_flags &= FIEMAP_FLAGS_COMPAT;
>   	incompat_flags = fieinfo->fi_flags & ~supported_flags;
>   	if (incompat_flags) {
>   		fieinfo->fi_flags = incompat_flags;
>   		return -EBADR;
>   	}
> -	return 0;
> +
> +	if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC)
> +		ret = filemap_write_and_wait(inode->i_mapping);
> +	return ret;

Since we could return an error from here.
I think we should again update the function description that
it could return a negative error value if filemap_write_and_wait()
fails. And also should document this in Documentation/*




>   }
>   EXPORT_SYMBOL(fiemap_prep);
>   
> @@ -209,9 +214,6 @@ static int ioctl_fiemap(struct file *filp, struct fiemap __user *ufiemap)
>   		       fieinfo.fi_extents_max * sizeof(struct fiemap_extent)))
>   		return -EFAULT;
>   
> -	if (fieinfo.fi_flags & FIEMAP_FLAG_SYNC)
> -		filemap_write_and_wait(inode->i_mapping);
> -
>   	error = inode->i_op->fiemap(inode, &fieinfo, fiemap.fm_start,
>   			fiemap.fm_length);
>   	fiemap.fm_flags = fieinfo.fi_flags;
> diff --git a/fs/iomap/fiemap.c b/fs/iomap/fiemap.c
> index 5e4e3520424da..fffd9eedfd880 100644
> --- a/fs/iomap/fiemap.c
> +++ b/fs/iomap/fiemap.c
> @@ -75,16 +75,10 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi,
>   	ctx.fi = fi;
>   	ctx.prev.type = IOMAP_HOLE;
>   
> -	ret = fiemap_prep(inode, fi, start, &len, FIEMAP_FLAG_SYNC);
> +	ret = fiemap_prep(inode, fi, start, &len, 0);
>   	if (ret)
>   		return ret;
>   
> -	if (fi->fi_flags & FIEMAP_FLAG_SYNC) {
> -		ret = filemap_write_and_wait(inode->i_mapping);
> -		if (ret)
> -			return ret;
> -	}
> -
>   	while (len > 0) {
>   		ret = iomap_apply(inode, start, len, IOMAP_REPORT, ops, &ctx,
>   				iomap_fiemap_actor);
> diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
> index 052c2da11e4d7..25b0d368ecdb2 100644
> --- a/fs/nilfs2/inode.c
> +++ b/fs/nilfs2/inode.c
> @@ -1006,7 +1006,7 @@ int nilfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   	unsigned int blkbits = inode->i_blkbits;
>   	int ret, n;
>   
> -	ret = fiemap_prep(inode, fieinfo, start, &len, FIEMAP_FLAG_SYNC);
> +	ret = fiemap_prep(inode, fieinfo, start, &len, 0);
>   	if (ret)
>   		return ret;
>   
> diff --git a/fs/ocfs2/extent_map.c b/fs/ocfs2/extent_map.c
> index 3744179b73fa1..a94852af5510d 100644
> --- a/fs/ocfs2/extent_map.c
> +++ b/fs/ocfs2/extent_map.c
> @@ -733,8 +733,6 @@ static int ocfs2_fiemap_inline(struct inode *inode, struct buffer_head *di_bh,
>   	return 0;
>   }
>   
> -#define OCFS2_FIEMAP_FLAGS	(FIEMAP_FLAG_SYNC)
> -
>   int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   		 u64 map_start, u64 map_len)
>   {
> @@ -746,8 +744,7 @@ int ocfs2_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   	struct buffer_head *di_bh = NULL;
>   	struct ocfs2_extent_rec rec;
>   
> -	ret = fiemap_prep(inode, fieinfo, map_start, &map_len,
> -			OCFS2_FIEMAP_FLAGS);
> +	ret = fiemap_prep(inode, fieinfo, map_start, &map_len, 0);
>   	if (ret)
>   		return ret;
>   
> diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
> index b5fec34105569..c7cb883c47b86 100644
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -462,10 +462,6 @@ static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
>   		return -EOPNOTSUPP;
>   
>   	old_cred = ovl_override_creds(inode->i_sb);
> -
> -	if (fieinfo->fi_flags & FIEMAP_FLAG_SYNC)
> -		filemap_write_and_wait(realinode->i_mapping);
> -
>   	err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
>   	revert_creds(old_cred);
>