+ shmem-set-shmem_writepage-variables-early.patch added to mm-unstable branch

+ shmem-set-shmem_writepage-variables-early.patch added to mm-unstable branch

[Andrew Morton]

The patch titled
     Subject: shmem: set shmem_writepage() variables early
has been added to the -mm mm-unstable branch.  Its filename is
     shmem-set-shmem_writepage-variables-early.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/shmem-set-shmem_writepage-variables-early.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Luis Chamberlain <mcgrof@kernel.org>
Subject: shmem: set shmem_writepage() variables early
Date: Thu, 9 Mar 2023 15:05:41 -0800

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.

Link: https://lkml.kernel.org/r/20230309230545.2930737-3-mcgrof@kernel.org
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Christian Brauner <brauner@kernel.org>
Cc: Adam Manzanares <a.manzanares@samsung.com>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Pankaj Raghav <p.raghav@samsung.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
---


--- a/mm/shmem.c~shmem-set-shmem_writepage-variables-early
+++ a/mm/shmem.c
@@ -1316,9 +1316,9 @@ 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;
 
@@ -1336,10 +1336,7 @@ static int shmem_writepage(struct page *
 		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)
_

Patches currently in -mm which might be from mcgrof@kernel.org are

shmem-remove-check-for-folio-lock-on-writepage.patch
shmem-set-shmem_writepage-variables-early.patch
shmem-move-reclaim-check-early-on-writepages.patch
shmem-skip-page-split-if-were-not-reclaiming.patch
shmem-update-documentation.patch
shmem-add-support-to-ignore-swap.patch