2020-05-30 09:31:07

by Huaisheng Ye

[permalink] [raw]
Subject: [PATCH] dm writecache: reinitialize lru in writeback instead of endio

From: Huaisheng Ye <[email protected]>

When wc_entry has been removed from wbl->list in writeback, it will
be not used again except waiting to be set free in writecache_free_entry.

That is a little of annoying, it has to reinitialize lru of wc_entry
in endio before calling writecache_free_entry.

Using list_del_init instead of list_del in writeback for simpler code.

Signed-off-by: Huaisheng Ye <[email protected]>
---
drivers/md/dm-writecache.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index 7bbc21b..66f3a3b 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -1519,7 +1519,6 @@ static void __writecache_endio_pmem(struct dm_writecache *wc, struct list_head *
e = wb->wc_list[i];
BUG_ON(!e->write_in_progress);
e->write_in_progress = false;
- INIT_LIST_HEAD(&e->lru);
if (!writecache_has_error(wc))
writecache_free_entry(wc, e);
BUG_ON(!wc->writeback_size);
@@ -1555,7 +1554,6 @@ static void __writecache_endio_ssd(struct dm_writecache *wc, struct list_head *l
do {
BUG_ON(!e->write_in_progress);
e->write_in_progress = false;
- INIT_LIST_HEAD(&e->lru);
if (!writecache_has_error(wc))
writecache_free_entry(wc, e);

@@ -1654,7 +1652,7 @@ static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeba
while (wbl->size) {
wbl->size--;
e = container_of(wbl->list.prev, struct wc_entry, lru);
- list_del(&e->lru);
+ list_del_init(&e->lru);

max_pages = e->wc_list_contiguous;

@@ -1685,7 +1683,7 @@ static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeba
if (!wc_add_block(wb, f, GFP_NOWAIT | __GFP_NOWARN))
break;
wbl->size--;
- list_del(&f->lru);
+ list_del_init(&f->lru);
wb->wc_list[wb->wc_list_n++] = f;
e = f;
}
@@ -1712,7 +1710,7 @@ static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writebac

wbl->size--;
e = container_of(wbl->list.prev, struct wc_entry, lru);
- list_del(&e->lru);
+ list_del_init(&e->lru);

n_sectors = e->wc_list_contiguous << (wc->block_size_bits - SECTOR_SHIFT);

@@ -1732,7 +1730,7 @@ static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writebac
wbl->size--;
f = container_of(wbl->list.prev, struct wc_entry, lru);
BUG_ON(f != e + 1);
- list_del(&f->lru);
+ list_del_init(&f->lru);
e = f;
}

--
1.8.3.1


2020-06-01 14:34:29

by Mikulas Patocka

[permalink] [raw]
Subject: Re: [PATCH] dm writecache: reinitialize lru in writeback instead of endio



On Sat, 30 May 2020, Huaisheng Ye wrote:

> From: Huaisheng Ye <[email protected]>
>
> When wc_entry has been removed from wbl->list in writeback, it will
> be not used again except waiting to be set free in writecache_free_entry.
>
> That is a little of annoying, it has to reinitialize lru of wc_entry
> in endio before calling writecache_free_entry.
>
> Using list_del_init instead of list_del in writeback for simpler code.
>
> Signed-off-by: Huaisheng Ye <[email protected]>

This patch doesn't fix anything, so I think we don't need it.

Actually, it's better to keep the list entry uninitialized, because it
helps us catch bugs where this uninitialized list entry could be used
improperly.

Mikulas

> ---
> drivers/md/dm-writecache.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
> index 7bbc21b..66f3a3b 100644
> --- a/drivers/md/dm-writecache.c
> +++ b/drivers/md/dm-writecache.c
> @@ -1519,7 +1519,6 @@ static void __writecache_endio_pmem(struct dm_writecache *wc, struct list_head *
> e = wb->wc_list[i];
> BUG_ON(!e->write_in_progress);
> e->write_in_progress = false;
> - INIT_LIST_HEAD(&e->lru);
> if (!writecache_has_error(wc))
> writecache_free_entry(wc, e);
> BUG_ON(!wc->writeback_size);
> @@ -1555,7 +1554,6 @@ static void __writecache_endio_ssd(struct dm_writecache *wc, struct list_head *l
> do {
> BUG_ON(!e->write_in_progress);
> e->write_in_progress = false;
> - INIT_LIST_HEAD(&e->lru);
> if (!writecache_has_error(wc))
> writecache_free_entry(wc, e);
>
> @@ -1654,7 +1652,7 @@ static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeba
> while (wbl->size) {
> wbl->size--;
> e = container_of(wbl->list.prev, struct wc_entry, lru);
> - list_del(&e->lru);
> + list_del_init(&e->lru);
>
> max_pages = e->wc_list_contiguous;
>
> @@ -1685,7 +1683,7 @@ static void __writecache_writeback_pmem(struct dm_writecache *wc, struct writeba
> if (!wc_add_block(wb, f, GFP_NOWAIT | __GFP_NOWARN))
> break;
> wbl->size--;
> - list_del(&f->lru);
> + list_del_init(&f->lru);
> wb->wc_list[wb->wc_list_n++] = f;
> e = f;
> }
> @@ -1712,7 +1710,7 @@ static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writebac
>
> wbl->size--;
> e = container_of(wbl->list.prev, struct wc_entry, lru);
> - list_del(&e->lru);
> + list_del_init(&e->lru);
>
> n_sectors = e->wc_list_contiguous << (wc->block_size_bits - SECTOR_SHIFT);
>
> @@ -1732,7 +1730,7 @@ static void __writecache_writeback_ssd(struct dm_writecache *wc, struct writebac
> wbl->size--;
> f = container_of(wbl->list.prev, struct wc_entry, lru);
> BUG_ON(f != e + 1);
> - list_del(&f->lru);
> + list_del_init(&f->lru);
> e = f;
> }
>
> --
> 1.8.3.1
>