linux-kernel - [PATCH v2 2/6] shmem: set shmem

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Date:   Thu,  9 Mar 2023 15:05:41 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     hughd@...gle.com, akpm@...ux-foundation.org, willy@...radead.org,
        brauner@...nel.org
Cc:     linux-mm@...ck.org, p.raghav@...sung.com, da.gomez@...sung.com,
        a.manzanares@...sung.com, dave@...olabs.net, yosryahmed@...gle.com,
        keescook@...omium.org, mcgrof@...nel.org, patches@...ts.linux.dev,
        linux-kernel@...r.kernel.org, David Hildenbrand <david@...hat.com>
Subject: [PATCH v2 2/6] shmem: set shmem_writepage() variables early

shmem_writepage() sets up variables typically used *after* a possible
huge page split. However even if that does happen the address space
mapping should not change, and the inode does not change either. So it
should be safe to set that from the very beginning.

This commit makes no functional changes.

Acked-by: David Hildenbrand <david@...hat.com>
Reviewed-by: Christian Brauner <brauner@...nel.org>
Signed-off-by: Luis Chamberlain <mcgrof@...nel.org>
---
 mm/shmem.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 7fff1a3af092..2b9ff585a553 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1334,9 +1334,9 @@ int shmem_unuse(unsigned int type)
 static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 {
 	struct folio *folio = page_folio(page);
-	struct shmem_inode_info *info;
-	struct address_space *mapping;
-	struct inode *inode;
+	struct address_space *mapping = folio->mapping;
+	struct inode *inode = mapping->host;
+	struct shmem_inode_info *info = SHMEM_I(inode);
 	swp_entry_t swap;
 	pgoff_t index;
 
@@ -1354,10 +1354,7 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
 		folio_clear_dirty(folio);
 	}
 
-	mapping = folio->mapping;
 	index = folio->index;
-	inode = mapping->host;
-	info = SHMEM_I(inode);
 	if (info->flags & VM_LOCKED)
 		goto redirty;
 	if (!total_swap_pages)
-- 
2.39.1