linux-kernel - Re: [PATCH v3] fs: dax: Adding new return type vm_fault

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Message-ID: <20180421213401.GF14610@bombadil.infradead.org>
Date:   Sat, 21 Apr 2018 14:34:01 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Souptick Joarder <jrdr.linux@...il.com>
Cc:     viro@...iv.linux.org.uk, mawilcox@...rosoft.com,
        ross.zwisler@...ux.intel.com, akpm@...ux-foundation.org,
        dan.j.williams@...el.com, mhocko@...e.com, jack@...e.cz,
        kirill.shutemov@...ux.intel.com, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] fs: dax: Adding new return type vm_fault_t

On Sun, Apr 22, 2018 at 02:35:29AM +0530, Souptick Joarder wrote:
> Use new return type vm_fault_t for fault handler. For
> now, this is just documenting that the function returns
> a VM_FAULT value rather than an errno. Once all instances
> are converted, vm_fault_t will become a distinct type.
> 
> commit 1c8f422059ae ("mm: change return type to vm_fault_t")
> 
> There was an existing bug inside dax_load_hole()
> if vm_insert_mixed had failed to allocate a page table,
> we'd return VM_FAULT_NOPAGE instead of VM_FAULT_OOM.
> With new vmf_insert_mixed() this issue is addressed.
> 
> vm_insert_mixed_mkwrite has inefficiency when it returns
> an error value, driver has to convert it to vm_fault_t
> type. With new vmf_insert_mixed_mkwrite() this limitation
> will be addressed.
> 
> As new function vmf_insert_mixed_mkwrite() only called
> from fs/dax.c, so keeping both the changes in a single
> patch.
> 
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>

Reviewed-by: Matthew Wilcox <mawilcox@...rosoft.com>

There's a couple of minor things which could be tidied up, but not worth
doing them as a revision to this patch.