* [PATCH 1/3 linux-next] Revert "mm,shmem: fix a typo in shmem_swapin_page()"
@ 2021-08-10 20:29 Yang Shi
2021-08-10 20:29 ` [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff" Yang Shi
2021-08-10 20:29 ` [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not" Yang Shi
0 siblings, 2 replies; 7+ messages in thread
From: Yang Shi @ 2021-08-10 20:29 UTC (permalink / raw)
To: hughd, ying.huang, linmiaohe, Andrew Morton
Cc: shy828301, linux-mm, linux-kernel
Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
is congested or not") doesn't stand anymore, so the commit could be just
reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
fix shmem_swapin() race with swapoff"), so the fix commit and this fix's fix
commit could be reverted as well.
Suggested-by: Hugh Dickins <hughd@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Yang Shi <shy828301@gmail.com>
---
This revert is for linux-next/-mm tree only since this commit has not
merged into Linus's tree yet.
mm/shmem.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index 1bea7f50825b..dcc07d14162e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1711,7 +1711,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
/* Prevent swapoff from happening to us. */
si = get_swap_device(swap);
if (!si) {
- error = -EINVAL;
+ error = EINVAL;
goto failed;
}
/* Look it up and read it in.. */
--
2.26.2
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff"
2021-08-10 20:29 [PATCH 1/3 linux-next] Revert "mm,shmem: fix a typo in shmem_swapin_page()" Yang Shi
@ 2021-08-10 20:29 ` Yang Shi
2021-08-10 23:14 ` Yang Shi
2021-08-10 20:29 ` [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not" Yang Shi
1 sibling, 1 reply; 7+ messages in thread
From: Yang Shi @ 2021-08-10 20:29 UTC (permalink / raw)
To: hughd, ying.huang, linmiaohe, Andrew Morton
Cc: shy828301, linux-mm, linux-kernel
Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
is congested or not") doesn't stand anymore, so the commit could be just
reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
fix shmem_swapin() race with swapoff"), so the fix commit could be just
reverted as well.
Suggested-by: Hugh Dickins <hughd@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Yang Shi <shy828301@gmail.com>
---
mm/shmem.c | 14 +-------------
1 file changed, 1 insertion(+), 13 deletions(-)
diff --git a/mm/shmem.c b/mm/shmem.c
index dcc07d14162e..d5427de5bf02 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1699,8 +1699,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
struct address_space *mapping = inode->i_mapping;
struct shmem_inode_info *info = SHMEM_I(inode);
struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
- struct swap_info_struct *si;
- struct page *page = NULL;
+ struct page *page;
swp_entry_t swap;
int error;
@@ -1708,12 +1707,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
swap = radix_to_swp_entry(*pagep);
*pagep = NULL;
- /* Prevent swapoff from happening to us. */
- si = get_swap_device(swap);
- if (!si) {
- error = EINVAL;
- goto failed;
- }
/* Look it up and read it in.. */
page = lookup_swap_cache(swap, NULL, 0);
if (!page) {
@@ -1775,8 +1768,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
swap_free(swap);
*pagep = page;
- if (si)
- put_swap_device(si);
return 0;
failed:
if (!shmem_confirm_swap(mapping, index, swap))
@@ -1787,9 +1778,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
put_page(page);
}
- if (si)
- put_swap_device(si);
-
return error;
}
--
2.26.2
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not"
2021-08-10 20:29 [PATCH 1/3 linux-next] Revert "mm,shmem: fix a typo in shmem_swapin_page()" Yang Shi
2021-08-10 20:29 ` [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff" Yang Shi
@ 2021-08-10 20:29 ` Yang Shi
2021-08-10 21:08 ` Hugh Dickins
1 sibling, 1 reply; 7+ messages in thread
From: Yang Shi @ 2021-08-10 20:29 UTC (permalink / raw)
To: hughd, ying.huang, linmiaohe, Andrew Morton
Cc: shy828301, linux-mm, linux-kernel
Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
is congested or not") doesn't stand anymore, so the commit could be just
reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
fix shmem_swapin() race with swapoff"). The fix was reverted by the
previous patch.
Suggested-by: Hugh Dickins <hughd@google.com>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Yang Shi <shy828301@gmail.com>
---
mm/swap_state.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 1a29b4f98208..8d4104242100 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -628,13 +628,6 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
if (!mask)
goto skip;
- /* Test swap type to make sure the dereference is safe */
- if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
- struct inode *inode = si->swap_file->f_mapping->host;
- if (inode_read_congested(inode))
- goto skip;
- }
-
do_poll = false;
/* Read a page_cluster sized and aligned cluster around offset. */
start_offset = offset & ~mask;
--
2.26.2
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not"
2021-08-10 20:29 ` [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not" Yang Shi
@ 2021-08-10 21:08 ` Hugh Dickins
2021-08-10 21:30 ` Yang Shi
0 siblings, 1 reply; 7+ messages in thread
From: Hugh Dickins @ 2021-08-10 21:08 UTC (permalink / raw)
To: Yang Shi
Cc: hughd, ying.huang, linmiaohe, Andrew Morton, linux-mm, linux-kernel
On Tue, 10 Aug 2021, Yang Shi wrote:
> Due to the change about how block layer detects congestion the
> justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
> is congested or not") doesn't stand anymore, so the commit could be just
> reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
> fix shmem_swapin() race with swapoff"). The fix was reverted by the
> previous patch.
>
> Suggested-by: Hugh Dickins <hughd@google.com>
> Cc: "Huang, Ying" <ying.huang@intel.com>
> Cc: Miaohe Lin <linmiaohe@huawei.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
Thanks for doing these,
Acked-by: Hugh Dickins <hughd@google.com>
to all three.
I guess 1/3 will vanish now, since what it's reverting has not yet gone
forward to Linus: it would have been nice for 2/3 to have mentioned that
what it's reverting is kindof buggy: but then you'd have to explain the
"kindof", and that takes more words than it's worth - maybe a lore Link
to the discussion?
But you've done the work that I've not yet got around to:
so thank you, and ignore my gripes.
Hugh
> ---
> mm/swap_state.c | 7 -------
> 1 file changed, 7 deletions(-)
>
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 1a29b4f98208..8d4104242100 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -628,13 +628,6 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> if (!mask)
> goto skip;
>
> - /* Test swap type to make sure the dereference is safe */
> - if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
> - struct inode *inode = si->swap_file->f_mapping->host;
> - if (inode_read_congested(inode))
> - goto skip;
> - }
> -
> do_poll = false;
> /* Read a page_cluster sized and aligned cluster around offset. */
> start_offset = offset & ~mask;
> --
> 2.26.2
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not"
2021-08-10 21:08 ` Hugh Dickins
@ 2021-08-10 21:30 ` Yang Shi
2021-08-10 21:57 ` Hugh Dickins
0 siblings, 1 reply; 7+ messages in thread
From: Yang Shi @ 2021-08-10 21:30 UTC (permalink / raw)
To: Hugh Dickins
Cc: Huang Ying, Miaohe Lin, Andrew Morton, Linux MM,
Linux Kernel Mailing List
On Tue, Aug 10, 2021 at 2:08 PM Hugh Dickins <hughd@google.com> wrote:
>
> On Tue, 10 Aug 2021, Yang Shi wrote:
>
> > Due to the change about how block layer detects congestion the
> > justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
> > is congested or not") doesn't stand anymore, so the commit could be just
> > reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
> > fix shmem_swapin() race with swapoff"). The fix was reverted by the
> > previous patch.
> >
> > Suggested-by: Hugh Dickins <hughd@google.com>
> > Cc: "Huang, Ying" <ying.huang@intel.com>
> > Cc: Miaohe Lin <linmiaohe@huawei.com>
> > Signed-off-by: Yang Shi <shy828301@gmail.com>
>
> Thanks for doing these,
> Acked-by: Hugh Dickins <hughd@google.com>
> to all three.
>
> I guess 1/3 will vanish now, since what it's reverting has not yet gone
> forward to Linus: it would have been nice for 2/3 to have mentioned that
> what it's reverting is kindof buggy: but then you'd have to explain the
> "kindof", and that takes more words than it's worth - maybe a lore Link
> to the discussion?
It is fine, I think this one is the best elaborated the problem:
https://lore.kernel.org/linux-mm/24187e5e-069-9f3f-cefe-39ac70783753@google.com/
>
> But you've done the work that I've not yet got around to:
> so thank you, and ignore my gripes.
>
> Hugh
>
> > ---
> > mm/swap_state.c | 7 -------
> > 1 file changed, 7 deletions(-)
> >
> > diff --git a/mm/swap_state.c b/mm/swap_state.c
> > index 1a29b4f98208..8d4104242100 100644
> > --- a/mm/swap_state.c
> > +++ b/mm/swap_state.c
> > @@ -628,13 +628,6 @@ struct page *swap_cluster_readahead(swp_entry_t entry, gfp_t gfp_mask,
> > if (!mask)
> > goto skip;
> >
> > - /* Test swap type to make sure the dereference is safe */
> > - if (likely(si->flags & (SWP_BLKDEV | SWP_FS_OPS))) {
> > - struct inode *inode = si->swap_file->f_mapping->host;
> > - if (inode_read_congested(inode))
> > - goto skip;
> > - }
> > -
> > do_poll = false;
> > /* Read a page_cluster sized and aligned cluster around offset. */
> > start_offset = offset & ~mask;
> > --
> > 2.26.2
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not"
2021-08-10 21:30 ` Yang Shi
@ 2021-08-10 21:57 ` Hugh Dickins
0 siblings, 0 replies; 7+ messages in thread
From: Hugh Dickins @ 2021-08-10 21:57 UTC (permalink / raw)
To: Yang Shi
Cc: Hugh Dickins, Huang Ying, Miaohe Lin, Andrew Morton, Linux MM,
Linux Kernel Mailing List
On Tue, 10 Aug 2021, Yang Shi wrote:
> On Tue, Aug 10, 2021 at 2:08 PM Hugh Dickins <hughd@google.com> wrote:
> >
> > I guess 1/3 will vanish now, since what it's reverting has not yet gone
> > forward to Linus: it would have been nice for 2/3 to have mentioned that
> > what it's reverting is kindof buggy: but then you'd have to explain the
> > "kindof", and that takes more words than it's worth - maybe a lore Link
> > to the discussion?
>
> It is fine, I think this one is the best elaborated the problem:
> https://lore.kernel.org/linux-mm/24187e5e-069-9f3f-cefe-39ac70783753@google.com/
Yes, that best elaborated the problem when I thought it was a problem, then
https://lore.kernel.org/linux-mm/e82380b9-3ad4-4a52-be50-6d45c7f2b5da@google.com/
explained why I later came to think that it wasn't a problem after all.
Hence "kindof" buggy: but good to be reverted anyway.
Whatever!
Thanks,
Hugh
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff"
2021-08-10 20:29 ` [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff" Yang Shi
@ 2021-08-10 23:14 ` Yang Shi
0 siblings, 0 replies; 7+ messages in thread
From: Yang Shi @ 2021-08-10 23:14 UTC (permalink / raw)
To: Hugh Dickins, Huang Ying, Miaohe Lin, Andrew Morton
Cc: Linux MM, Linux Kernel Mailing List
On Tue, Aug 10, 2021 at 1:29 PM Yang Shi <shy828301@gmail.com> wrote:
>
> Due to the change about how block layer detects congestion the
> justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
> is congested or not") doesn't stand anymore, so the commit could be just
> reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
> fix shmem_swapin() race with swapoff"), so the fix commit could be just
> reverted as well.
The updated commit log per the discussion with Hugh:
Due to the change about how block layer detects congestion the
justification of commit 8fd2e0b505d1 ("mm: swap: check if swap backing device
is congested or not") doesn't stand anymore, so the commit could be just
reverted in order to solve the race reported by commit 2efa33fc7f6e ("mm/shmem:
fix shmem_swapin() race with swapoff"), so the fix commit could be just
reverted as well.
And that fix is also kind of buggy as discussed by [1] and [2].
[1] https://lore.kernel.org/linux-mm/24187e5e-069-9f3f-cefe-39ac70783753@google.com/
[2] https://lore.kernel.org/linux-mm/e82380b9-3ad4-4a52-be50-6d45c7f2b5da@google.com/
>
> Suggested-by: Hugh Dickins <hughd@google.com>
> Cc: "Huang, Ying" <ying.huang@intel.com>
> Cc: Miaohe Lin <linmiaohe@huawei.com>
> Signed-off-by: Yang Shi <shy828301@gmail.com>
> ---
> mm/shmem.c | 14 +-------------
> 1 file changed, 1 insertion(+), 13 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index dcc07d14162e..d5427de5bf02 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1699,8 +1699,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> struct address_space *mapping = inode->i_mapping;
> struct shmem_inode_info *info = SHMEM_I(inode);
> struct mm_struct *charge_mm = vma ? vma->vm_mm : NULL;
> - struct swap_info_struct *si;
> - struct page *page = NULL;
> + struct page *page;
> swp_entry_t swap;
> int error;
>
> @@ -1708,12 +1707,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> swap = radix_to_swp_entry(*pagep);
> *pagep = NULL;
>
> - /* Prevent swapoff from happening to us. */
> - si = get_swap_device(swap);
> - if (!si) {
> - error = EINVAL;
> - goto failed;
> - }
> /* Look it up and read it in.. */
> page = lookup_swap_cache(swap, NULL, 0);
> if (!page) {
> @@ -1775,8 +1768,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> swap_free(swap);
>
> *pagep = page;
> - if (si)
> - put_swap_device(si);
> return 0;
> failed:
> if (!shmem_confirm_swap(mapping, index, swap))
> @@ -1787,9 +1778,6 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index,
> put_page(page);
> }
>
> - if (si)
> - put_swap_device(si);
> -
> return error;
> }
>
> --
> 2.26.2
>
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2021-08-10 23:15 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-08-10 20:29 [PATCH 1/3 linux-next] Revert "mm,shmem: fix a typo in shmem_swapin_page()" Yang Shi
2021-08-10 20:29 ` [PATCH 2/3] Revert "mm/shmem: fix shmem_swapin() race with swapoff" Yang Shi
2021-08-10 23:14 ` Yang Shi
2021-08-10 20:29 ` [PATCH 3/3] Revert "mm: swap: check if swap backing device is congested or not" Yang Shi
2021-08-10 21:08 ` Hugh Dickins
2021-08-10 21:30 ` Yang Shi
2021-08-10 21:57 ` Hugh Dickins
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