linux-kernel - Re: [PATCH 3/7] fsdax: Copy data before write

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Date:   Mon, 8 Feb 2021 16:14:19 +0100
From:   Christoph Hellwig <hch@....de>
To:     Shiyang Ruan <ruansy.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-fsdevel@...r.kernel.org,
        darrick.wong@...cle.com, dan.j.williams@...el.com,
        willy@...radead.org, jack@...e.cz, viro@...iv.linux.org.uk,
        linux-btrfs@...r.kernel.org, ocfs2-devel@....oracle.com,
        david@...morbit.com, hch@....de, rgoldwyn@...e.de
Subject: Re: [PATCH 3/7] fsdax: Copy data before write

>  	switch (iomap.type) {
>  	case IOMAP_MAPPED:
> +cow:
>  		if (iomap.flags & IOMAP_F_NEW) {
>  			count_vm_event(PGMAJFAULT);
>  			count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
>  			major = VM_FAULT_MAJOR;
>  		}
>  		error = dax_iomap_direct_access(&iomap, pos, PAGE_SIZE,
> -						NULL, &pfn);
> +						&kaddr, &pfn);

Any chance you could look into factoring out this code into a helper
to avoid the goto magic, which is a little too convoluted?

>  	switch (iomap.type) {
>  	case IOMAP_MAPPED:
> +cow:
>  		error = dax_iomap_direct_access(&iomap, pos, PMD_SIZE,
> -						NULL, &pfn);
> +						&kaddr, &pfn);
>  		if (error < 0)
>  			goto finish_iomap;
>  
>  		entry = dax_insert_entry(&xas, mapping, vmf, entry, pfn,
>  						DAX_PMD, write && !sync);
>  
> +		if (srcmap.type != IOMAP_HOLE) {

Same here.