Re: [PATCH] iomap: add dirty page control to iomap_zero_iter
From: Chi Zhiling
Date: Mon May 11 2026 - 05:36:45 EST
On 5/11/26 16:57, Christoph Hellwig wrote:
On Sun, May 10, 2026 at 02:47:37PM +0800, Chi Zhiling wrote:
From: Chi Zhiling <chizhiling@xxxxxxxxxx>
This patch prepares the iomap framework for exFAT's upcoming migration to
iomap. During testing of the exFAT iomap branch with xfstests generic/299
on a VM with 8GB RAM and a 40GB disk, system unresponsiveness was observed.
iomap_zero_iter() lacked dirty page throttling, which could cause memory
pressure when exFAT's valid_size mechanism triggers large-scale zeroing
operations during writes beyond valid_size.
Align iomap_zero_iter() with iomap_write_iter() by adding
balance_dirty_pages_ratelimited() to throttle dirty page generation during
large zeroing operations. Also add cond_resched() to provide voluntary
rescheduling points during long-running loops.
The balance_dirty_pages_ratelimited looks good. Now with lazy preempt
we really should not need more cond_resched calls, though.
Okay, will drop it in next version.
Thanks,
---end quoted text---
Signed-off-by: Chi Zhiling <chizhiling@xxxxxxxxxx>
Cc: Namjae Jeon <linkinjeon@xxxxxxxxxx>
---
exFAT iomap migration:
https://lore.kernel.org/linux-fsdevel/20260507124238.7313-1-linkinjeon@xxxxxxxxxx/
fs/iomap/buffered-io.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index d7b648421a70..f6955786c8ad 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -1543,6 +1543,8 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
size_t offset;
bool ret;
+ balance_dirty_pages_ratelimited(iter->inode->i_mapping);
+
bytes = min_t(u64, SIZE_MAX, bytes);
status = iomap_write_begin(iter, write_ops, &folio, &offset,
&bytes);
@@ -1571,6 +1573,8 @@ static int iomap_zero_iter(struct iomap_iter *iter, bool *did_zero,
if (WARN_ON_ONCE(!ret))
return -EIO;
+ cond_resched();
+
status = iomap_iter_advance(iter, bytes);
if (status)
break;
--
2.43.0