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writeback: reset dirtied_when when switching wbs

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When switching a dirty inode to another wb, inode_do_switch_wbs() puts
it at the newest end of the target b_dirty list instead of searching
for its sorted position. This requires updating dirtied_when, which
move_expired_inodes() uses to decide where to stop scanning.

However, the switch updates dirtied_time_when instead. This leaves
b_dirty out of order and can make the scan stop before reaching older
inodes. It also resets the lazytime expiration timestamp, potentially
delaying timestamp writeback.

Update dirtied_when instead, preserving both the constant-time insertion
and the lazytime expiration timestamp. Correct the field name in the
comment and document the distinction between the two inode timestamps.

Fixes: 9a6ebbdbd4 ("writeback: Avoid excessively long inode switching times")
Cc: stable@vger.kernel.org
Signed-off-by: Julian Sun <sunjunchao@bytedance.com>
Link: https://patch.msgid.link/20261016115230.3640770-2-sunjunchao@bytedance.com
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
This commit is contained in:
Julian Sun 2026-10-16 19:52:29 +08:00 committed by Christian Brauner
parent 7459c02187
commit 13b9a606dd
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
2 changed files with 6 additions and 4 deletions
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6
fs/fs-writeback.c
View File

@ -468,12 +468,12 @@ static bool inode_do_switch_wbs(struct inode *inode,
if (inode_state_read(inode) & I_DIRTY_ALL) {
/*
* We need to keep b_dirty list sorted by
* dirtied_time_when. However properly sorting the
* dirtied_when. However properly sorting the
* inode in the list gets too expensive when switching
* many inodes. So just attach inode at the end of the
* dirty list and clobber the dirtied_time_when.
* dirty list and clobber the dirtied_when.
*/
inode->dirtied_time_when = jiffies;
inode->dirtied_when = jiffies;
inode_io_list_move_locked(inode, new_wb,
&new_wb->b_dirty);
} else {

4
include/linux/fs.h
View File

@ -815,7 +815,9 @@ struct inode {
/* 32-bit hole */
struct rw_semaphore i_rwsem;
unsigned long dirtied_when; /* jiffies of first dirtying */
/* Timestamp for writeback list ordering and age checks (jiffies). */
unsigned long dirtied_when;
/* Start time for deciding when lazytime updates need writeback (jiffies). */
unsigned long dirtied_time_when;
struct hlist_node i_hash;