linux-kernel - Query on mm/folio-compat: pagecache_get

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Message-ID: <Y+vRpvwNgwDB4MS0@ubun2204.myguest.virtualbox.org>
Date:   Tue, 14 Feb 2023 23:53:34 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, willy@...radead.org
Cc:     Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>,
        Deepak R Varma <drv@...lo.com>
Subject: Query on mm/folio-compat: pagecache_get_page

Hello,
Could someone comment if it is safe to access the page member variable as
written on line #100 when folio is NULL as returned from the
__filemap_get_folio() function call? Is this kind of intentional page-fault
trigger for the system to handle a new/fresh page allocation?

	  2         folio = __filemap_get_folio(mapping, index, fgp_flags, gfp);
	  1         if (!folio || xa_is_value(folio))
	100                 return &folio->page;
	  1         return folio_file_page(folio, index);

The code is part of commit ID c5255b421fd04

Thank you,
./drv