linux-kernel - [PATCH v5 01/24] ext4/xfs: add page refcount helper

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Message-Id: <20220128002614.6136-2-logang@deltatee.com>
Date:   Thu, 27 Jan 2022 17:25:51 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Jakowski Andrzej <andrzej.jakowski@...el.com>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@...il.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Alex Sierra <alex.sierra@....com>,
        Theodore Ts'o <tytso@....edu>,
        "Darrick J . Wong" <djwong@...nel.org>
Subject: [PATCH v5 01/24] ext4/xfs: add page refcount helper

From: Ralph Campbell <rcampbell@...dia.com>

There are several places where ZONE_DEVICE struct pages assume a reference
count == 1 means the page is idle and free. Instead of open coding this,
add a helper function to hide this detail.

Signed-off-by: Ralph Campbell <rcampbell@...dia.com>
Signed-off-by: Alex Sierra <alex.sierra@....com>
Reviewed-by: Christoph Hellwig <hch@....de>
Acked-by: Theodore Ts'o <tytso@....edu>
Acked-by: Darrick J. Wong <djwong@...nel.org>
---
 fs/dax.c            |  4 ++--
 fs/ext4/inode.c     |  5 +----
 fs/fuse/dax.c       |  4 +---
 fs/xfs/xfs_file.c   |  4 +---
 include/linux/dax.h | 10 ++++++++++
 5 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index cd03485867a7..d9b856cf6436 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -369,7 +369,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
 	for_each_mapped_pfn(entry, pfn) {
 		struct page *page = pfn_to_page(pfn);
 
-		WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
+		WARN_ON_ONCE(trunc && !dax_page_unused(page));
 		WARN_ON_ONCE(page->mapping && page->mapping != mapping);
 		page->mapping = NULL;
 		page->index = 0;
@@ -383,7 +383,7 @@ static struct page *dax_busy_page(void *entry)
 	for_each_mapped_pfn(entry, pfn) {
 		struct page *page = pfn_to_page(pfn);
 
-		if (page_ref_count(page) > 1)
+		if (!dax_page_unused(page))
 			return page;
 	}
 	return NULL;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 5f79d265d06a..99e3ed7bcd06 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3899,10 +3899,7 @@ int ext4_break_layouts(struct inode *inode)
 		if (!page)
 			return 0;
 
-		error = ___wait_var_event(&page->_refcount,
-				atomic_read(&page->_refcount) == 1,
-				TASK_INTERRUPTIBLE, 0, 0,
-				ext4_wait_dax_page(inode));
+		error = dax_wait_page(inode, page, ext4_wait_dax_page);
 	} while (error == 0);
 
 	return error;
diff --git a/fs/fuse/dax.c b/fs/fuse/dax.c
index 182b24a14804..f8b3f30d2303 100644
--- a/fs/fuse/dax.c
+++ b/fs/fuse/dax.c
@@ -676,9 +676,7 @@ static int __fuse_dax_break_layouts(struct inode *inode, bool *retry,
 		return 0;
 
 	*retry = true;
-	return ___wait_var_event(&page->_refcount,
-			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
-			0, 0, fuse_wait_dax_page(inode));
+	return dax_wait_page(inode, page, fuse_wait_dax_page);
 }
 
 /* dmap_end == 0 leads to unmapping of whole file */
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 22ad207bedf4..57a440666935 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -859,9 +859,7 @@ xfs_break_dax_layouts(
 		return 0;
 
 	*retry = true;
-	return ___wait_var_event(&page->_refcount,
-			atomic_read(&page->_refcount) == 1, TASK_INTERRUPTIBLE,
-			0, 0, xfs_wait_dax_page(inode));
+	return dax_wait_page(inode, page, xfs_wait_dax_page);
 }
 
 int
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 9fc5f99a0ae2..479939b3be40 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -201,6 +201,16 @@ static inline bool dax_mapping(struct address_space *mapping)
 	return mapping->host && IS_DAX(mapping->host);
 }
 
+static inline bool dax_page_unused(struct page *page)
+{
+	return page_ref_count(page) == 1;
+}
+
+#define dax_wait_page(_inode, _page, _wait_cb)				\
+	___wait_var_event(&(_page)->_refcount,				\
+		dax_page_unused(_page),				\
+		TASK_INTERRUPTIBLE, 0, 0, _wait_cb(_inode))
+
 #ifdef CONFIG_DEV_DAX_HMEM_DEVICES
 void hmem_register_device(int target_nid, struct resource *r);
 #else
-- 
2.30.2