On Tue, 2 Sep 2025 11:52:50 +0200 Aleksandr Nogikh <nogikh@xxxxxxxxxx> wrote:
> Hi,
>
> When can the patch be expected to reach linux-next?
> Syzbot can't build/boot the tree for more than 12 days already :(
Please don't top-post - it messes things up so much.
There's nothing I can reasonably do about this - it's fixing an issue
that's coming in from Miklos's tree and perhaps he's offline.
Perhaps Stephen can directly add it to linux-next for a while?
From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
To: linux-fsdevel@xxxxxxxxxxxxxxx, linux-mm@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
Cc: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>, "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, David Hildenbrand <david@xxxxxxxxxx>, Miklos Szeredi <mszeredi@xxxxxxxxxx>, Joanne Koong <joannelkoong@xxxxxxxxx>
Subject: [PATCH] mm: fix lockdep issues in writeback handling
Date: Tue, 26 Aug 2025 15:09:48 +0200
Sender: owner-linux-mm@xxxxxxxxx
X-Mailer: git-send-email 2.34.1
Commit 167f21a81a9c ("mm: remove BDI_CAP_WRITEBACK_ACCT") removed
BDI_CAP_WRITEBACK_ACCT flag and refactored code that depend on it.
Unfortunately it also moved some variable intialization out of guarded
scope in writeback handling, what triggers a true lockdep warning. Fix
this by moving initialization to the proper place.
Fixes: 167f21a81a9c ("mm: remove BDI_CAP_WRITEBACK_ACCT")
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
---
mm/page-writeback.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 99e80bdb3084..3887ac2e6475 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2984,7 +2984,7 @@ bool __folio_end_writeback(struct folio *folio)
if (mapping && mapping_use_writeback_tags(mapping)) {
struct inode *inode = mapping->host;
- struct bdi_writeback *wb = inode_to_wb(inode);
+ struct bdi_writeback *wb;
unsigned long flags;
xa_lock_irqsave(&mapping->i_pages, flags);
@@ -2992,6 +2992,7 @@ bool __folio_end_writeback(struct folio *folio)
__xa_clear_mark(&mapping->i_pages, folio_index(folio),
PAGECACHE_TAG_WRITEBACK);
+ wb = inode_to_wb(inode);
wb_stat_mod(wb, WB_WRITEBACK, -nr);
__wb_writeout_add(wb, nr);
if (!mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK)) {
@@ -3024,7 +3025,7 @@ void __folio_start_writeback(struct folio *folio, bool keep_write)
if (mapping && mapping_use_writeback_tags(mapping)) {
XA_STATE(xas, &mapping->i_pages, folio_index(folio));
struct inode *inode = mapping->host;
- struct bdi_writeback *wb = inode_to_wb(inode);
+ struct bdi_writeback *wb;
unsigned long flags;
bool on_wblist;
@@ -3035,6 +3036,7 @@ void __folio_start_writeback(struct folio *folio, bool keep_write)
on_wblist = mapping_tagged(mapping, PAGECACHE_TAG_WRITEBACK);
xas_set_mark(&xas, PAGECACHE_TAG_WRITEBACK);
+ wb = inode_to_wb(inode);
wb_stat_mod(wb, WB_WRITEBACK, nr);
if (!on_wblist) {
wb_inode_writeback_start(wb);
--
2.34.1
