linux-ext4 - Re: [PATCH v4 10/12] dax: add struct iomap based DAX PMD support

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Message-ID: <20161005055020.GB20752@quack2.suse.cz>
Date:   Wed, 5 Oct 2016 07:50:20 +0200
From:   Jan Kara <jack@...e.cz>
To:     Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:     Jan Kara <jack@...e.cz>, linux-kernel@...r.kernel.org,
        Theodore Ts'o <tytso@....edu>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.com>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-nvdimm@...ts.01.org,
        linux-xfs@...r.kernel.org
Subject: Re: [PATCH v4 10/12] dax: add struct iomap based DAX PMD support

On Tue 04-10-16 09:39:48, Ross Zwisler wrote:
> > The gfp_mask that propagates from __do_fault() or do_page_mkwrite() is fine
> > because at that point it is correct. But once we grab filesystem locks
> > which are not reclaim safe, we should update vmf->gfp_mask we pass further
> > down into DAX code to not contain __GFP_FS (that's a bug we apparently have
> > there). And inside DAX code, we definitely are not generally safe to add
> > __GFP_FS to mapping_gfp_mask(). Maybe we'd be better off propagating struct
> > vm_fault into this function, using passed gfp_mask there and make sure
> > callers update gfp_mask as appropriate.
> 
> Yep, that makes sense to me.  In reviewing your set it also occurred to me that
> we might want to stick a struct vm_area_struct *vma pointer in the vmf, since
> you always need a vma when you are using a vmf, but we pass them as a pair
> everywhere.

Actually, vma pointer will be in struct vm_fault after my DAX
write-protection series. So once that lands, we can clean up whatever
duplicit function parameters...

								Honza

-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR
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