Re: [PATCH 03/13] filemap: assign current->backing_dev_info in generic_perform_write

[Xiubo Li <xiubli@redhat.com>]

On 5/19/23 17:35, Christoph Hellwig wrote:
> Move the assignment to current->backing_dev_info from the callers into
> generic_perform_write to reduce boiler plate code and reduce the scope
> to just around the page dirtying loop.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>   fs/ceph/file.c | 4 ----
>   fs/ext4/file.c | 3 ---
>   fs/f2fs/file.c | 2 --
>   fs/nfs/file.c  | 5 +----
>   mm/filemap.c   | 2 ++
>   5 files changed, 3 insertions(+), 13 deletions(-)
>
> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> index feeb9882ef635a..767f4dfe7def64 100644
> --- a/fs/ceph/file.c
> +++ b/fs/ceph/file.c
> @@ -1791,9 +1791,6 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
>   	else
>   		ceph_start_io_write(inode);
>   
> -	/* We can write back this queue in page reclaim */
> -	current->backing_dev_info = inode_to_bdi(inode);
> -
>   	if (iocb->ki_flags & IOCB_APPEND) {
>   		err = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE, false);
>   		if (err < 0)
> @@ -1938,7 +1935,6 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
>   		ceph_end_io_write(inode);
>   out_unlocked:
>   	ceph_free_cap_flush(prealloc_cf);
> -	current->backing_dev_info = NULL;
>   	return written ? written : err;
>   }
>   
> diff --git a/fs/ext4/file.c b/fs/ext4/file.c
> index 50824831d31def..3cb83a3e2e4a2a 100644
> --- a/fs/ext4/file.c
> +++ b/fs/ext4/file.c
> @@ -29,7 +29,6 @@
>   #include <linux/pagevec.h>
>   #include <linux/uio.h>
>   #include <linux/mman.h>
> -#include <linux/backing-dev.h>
>   #include "ext4.h"
>   #include "ext4_jbd2.h"
>   #include "xattr.h"
> @@ -285,9 +284,7 @@ static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
>   	if (ret <= 0)
>   		goto out;
>   
> -	current->backing_dev_info = inode_to_bdi(inode);
>   	ret = generic_perform_write(iocb, from);
> -	current->backing_dev_info = NULL;
>   
>   out:
>   	inode_unlock(inode);
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 9e3855e43a7a63..7134fe8bd008cb 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -4517,9 +4517,7 @@ static ssize_t f2fs_buffered_write_iter(struct kiocb *iocb,
>   	if (iocb->ki_flags & IOCB_NOWAIT)
>   		return -EOPNOTSUPP;
>   
> -	current->backing_dev_info = inode_to_bdi(inode);
>   	ret = generic_perform_write(iocb, from);
> -	current->backing_dev_info = NULL;
>   
>   	if (ret > 0) {
>   		f2fs_update_iostat(F2FS_I_SB(inode), inode,
> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
> index 3cc87ae8473356..e8bb4c48a3210a 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -648,11 +648,8 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from)
>   	since = filemap_sample_wb_err(file->f_mapping);
>   	nfs_start_io_write(inode);
>   	result = generic_write_checks(iocb, from);
> -	if (result > 0) {
> -		current->backing_dev_info = inode_to_bdi(inode);
> +	if (result > 0)
>   		result = generic_perform_write(iocb, from);
> -		current->backing_dev_info = NULL;
> -	}
>   	nfs_end_io_write(inode);
>   	if (result <= 0)
>   		goto out;
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 4d0ec2fa1c7070..bf693ad1da1ece 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3892,6 +3892,7 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
>   	long status = 0;
>   	ssize_t written = 0;
>   
> +	current->backing_dev_info = inode_to_bdi(mapping->host);
>   	do {
>   		struct page *page;
>   		unsigned long offset;	/* Offset into pagecache page */
> @@ -3956,6 +3957,7 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i)
>   
>   		balance_dirty_pages_ratelimited(mapping);
>   	} while (iov_iter_count(i));
> +	current->backing_dev_info = NULL;
>   
>   	if (!written)
>   		return status;

LGTM.

Reviewed-by: Xiubo Li <xiubli@redhat.com>

Thanks

- Xiubo