linux-kernel - Re: [PATCH v2.1 1/8] fsdax: introduce page->share for fsdax in reflink mode

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Date:   Fri, 2 Dec 2022 12:18:00 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc:     <linux-kernel@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        <nvdimm@...ts.linux.dev>, <linux-fsdevel@...r.kernel.org>,
        <djwong@...nel.org>, <david@...morbit.com>,
        <dan.j.williams@...el.com>
Subject: Re: [PATCH v2.1 1/8] fsdax: introduce page->share for fsdax in
 reflink mode

On Fri, 2 Dec 2022 09:23:11 +0000 Shiyang Ruan <ruansy.fnst@...itsu.com> wrote:

> fsdax page is used not only when CoW, but also mapread. To make the it
> easily understood, use 'share' to indicate that the dax page is shared
> by more than one extent.  And add helper functions to use it.
> 
> Also, the flag needs to be renamed to PAGE_MAPPING_DAX_SHARED.
> 

For those who are wondering what changed, I queued the below incremental
patch.


From: Shiyang Ruan <ruansy.fnst@...itsu.com>
Subject: fsdax: introduce page->share for fsdax in reflink mode
Date: Fri, 2 Dec 2022 09:23:11 +0000

rename several functions

Link: https://lkml.kernel.org/r/1669972991-246-1-git-send-email-ruansy.fnst@fujitsu.com
Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc: Alistair Popple <apopple@...dia.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Darrick J. Wong <djwong@...nel.org>
Cc: Dave Chinner <david@...morbit.com>
Cc: Jason Gunthorpe <jgg@...dia.com>
Cc: John Hubbard <jhubbard@...dia.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 fs/dax.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

--- a/fs/dax.c~fsdax-introduce-page-share-for-fsdax-in-reflink-mode-fix
+++ a/fs/dax.c
@@ -334,7 +334,7 @@ static unsigned long dax_end_pfn(void *e
 	for (pfn = dax_to_pfn(entry); \
 			pfn < dax_end_pfn(entry); pfn++)
 
-static inline bool dax_mapping_is_shared(struct page *page)
+static inline bool dax_page_is_shared(struct page *page)
 {
 	return (unsigned long)page->mapping == PAGE_MAPPING_DAX_SHARED;
 }
@@ -343,7 +343,7 @@ static inline bool dax_mapping_is_shared
  * Set the page->mapping with PAGE_MAPPING_DAX_SHARED flag, increase the
  * refcount.
  */
-static inline void dax_mapping_set_shared(struct page *page)
+static inline void dax_page_bump_sharing(struct page *page)
 {
 	if ((uintptr_t)page->mapping != PAGE_MAPPING_DAX_SHARED) {
 		/*
@@ -357,7 +357,7 @@ static inline void dax_mapping_set_share
 	page->share++;
 }
 
-static inline unsigned long dax_mapping_decrease_shared(struct page *page)
+static inline unsigned long dax_page_drop_sharing(struct page *page)
 {
 	return --page->share;
 }
@@ -381,7 +381,7 @@ static void dax_associate_entry(void *en
 		struct page *page = pfn_to_page(pfn);
 
 		if (shared) {
-			dax_mapping_set_shared(page);
+			dax_page_bump_sharing(page);
 		} else {
 			WARN_ON_ONCE(page->mapping);
 			page->mapping = mapping;
@@ -402,9 +402,9 @@ static void dax_disassociate_entry(void
 		struct page *page = pfn_to_page(pfn);
 
 		WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
-		if (dax_mapping_is_shared(page)) {
+		if (dax_page_is_shared(page)) {
 			/* keep the shared flag if this page is still shared */
-			if (dax_mapping_decrease_shared(page) > 0)
+			if (dax_page_drop_sharing(page) > 0)
 				continue;
 		} else
 			WARN_ON_ONCE(page->mapping && page->mapping != mapping);
_