linux-kernel - [PATCH v7 8/8] fsdax: add exception for reflinked files

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Date:   Fri, 24 Sep 2021 21:09:59 +0800
From:   Shiyang Ruan <ruansy.fnst@...itsu.com>
To:     <linux-kernel@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        <nvdimm@...ts.linux.dev>, <linux-mm@...ck.org>,
        <linux-fsdevel@...r.kernel.org>
CC:     <djwong@...nel.org>, <dan.j.williams@...el.com>,
        <david@...morbit.com>, <hch@...radead.org>, <jane.chu@...cle.com>
Subject: [PATCH v7 8/8] fsdax: add exception for reflinked files

For reflinked files, one dax page may be associated more than once with
different fime mapping and index.  It will report warning.  Now, since
we have introduced dax-RMAP for this case and also have to keep its
functionality for other filesystems who are not support rmap, I add this
exception here.

Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
---
 fs/dax.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 2536c105ec7f..1a57211b1bc9 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -352,9 +352,10 @@ static void dax_associate_entry(void *entry, struct address_space *mapping,
 	for_each_mapped_pfn(entry, pfn) {
 		struct page *page = pfn_to_page(pfn);
 
-		WARN_ON_ONCE(page->mapping);
-		page->mapping = mapping;
-		page->index = index + i++;
+		if (!page->mapping) {
+			page->mapping = mapping;
+			page->index = index + i++;
+		}
 	}
 }
 
@@ -370,9 +371,10 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
 		struct page *page = pfn_to_page(pfn);
 
 		WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
-		WARN_ON_ONCE(page->mapping && page->mapping != mapping);
-		page->mapping = NULL;
-		page->index = 0;
+		if (page->mapping == mapping) {
+			page->mapping = NULL;
+			page->index = 0;
+		}
 	}
 }
 
-- 
2.33.0