5.15-stable review patch. If anyone has any objections, please let me know.
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From: Jan Kara jack@suse.cz
[ Upstream commit 66c14dccd810d42ec5c73bb8a9177489dfd62278 ]
process_inode_switch_wbs_work() can be switching over 100 inodes to a different cgroup. Since switching an inode requires counting all dirty & under-writeback pages in the address space of each inode, this can take a significant amount of time. Add a possibility to reschedule after processing each inode to avoid softlockups.
Acked-by: Tejun Heo tj@kernel.org Signed-off-by: Jan Kara jack@suse.cz Signed-off-by: Christian Brauner brauner@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/fs-writeback.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index cb3f1790a296e..3b002ac407434 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -475,6 +475,7 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) */ down_read(&bdi->wb_switch_rwsem);
+ inodep = isw->inodes; /* * By the time control reaches here, RCU grace period has passed * since I_WB_SWITCH assertion and all wb stat update transactions @@ -485,6 +486,7 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) * gives us exclusion against all wb related operations on @inode * including IO list manipulations and stat updates. */ +relock: if (old_wb < new_wb) { spin_lock(&old_wb->list_lock); spin_lock_nested(&new_wb->list_lock, SINGLE_DEPTH_NESTING); @@ -493,10 +495,17 @@ static void inode_switch_wbs_work_fn(struct work_struct *work) spin_lock_nested(&old_wb->list_lock, SINGLE_DEPTH_NESTING); }
- for (inodep = isw->inodes; *inodep; inodep++) { + while (*inodep) { WARN_ON_ONCE((*inodep)->i_wb != old_wb); if (inode_do_switch_wbs(*inodep, old_wb, new_wb)) nr_switched++; + inodep++; + if (*inodep && need_resched()) { + spin_unlock(&new_wb->list_lock); + spin_unlock(&old_wb->list_lock); + cond_resched(); + goto relock; + } }
spin_unlock(&new_wb->list_lock);