[PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[Naohiro Aota]

commit 524272607e88 ("btrfs: Handle delalloc error correctly to avoid
ordered extent hang") introduced btrfs_cleanup_ordered_extents() to cleanup
submitted ordered extents. However, it does not clear the ordered bit
(Private2) of coresponding pages. Thus, the following BUG occurs from
free_pages_check_bad() (on btrfs/125 with nospace_cache).

BUG: Bad page state in process btrfs  pfn:3fa787
page:ffffdf2acfe9e1c0 count:0 mapcount:0 mapping:          (null) index:0xd
flags: 0x8000000000002008(uptodate|private_2)
raw: 8000000000002008 0000000000000000 000000000000000d 00000000ffffffff
raw: ffffdf2acf5c1b20 ffffb443802238b0 0000000000000000 0000000000000000
page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
bad because of flags: 0x2000(private_2)

This patch clear the flag as same as other places calling
btrfs_dec_test_ordered_pending() for every page in the specified range.

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
Cc: <stable@vger.kernel.org> # 4.12
---
 fs/btrfs/inode.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 24bcd5cd9cf2..ae4c0a1bef38 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -135,6 +135,18 @@ static inline void btrfs_cleanup_ordered_extents(struct inode *inode,
 						 const u64 offset,
 						 const u64 bytes)
 {
+	unsigned long index = offset >> PAGE_SHIFT;
+	unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
+	struct page *page;
+
+	while (index <= end_index) {
+		page = find_get_page(inode->i_mapping, index);
+		index++;
+		if (!page)
+			continue;
+		ClearPagePrivate2(page);
+		put_page(page);
+	}
 	return __endio_write_update_ordered(inode, offset + PAGE_SIZE,
 					    bytes - PAGE_SIZE, false);
 }

[PATCH 2/2] btrfs: finish ordered extent cleaning if no progress is found

[Naohiro Aota]

__endio_write_update_ordered() repeats the search until it reaches the end
of the specified range. This works well with direct IO path, because before
the function is called, it's ensured that there are ordered extents filling
whole the range. It's not the case, however, when it's called from
run_delalloc_range(): it is possible to have error in the midle of the loop
in e.g. run_delalloc_nocow(), so that there exisits the range not covered
by any ordered extents. By cleaning such "uncomplete" range,
__endio_write_update_ordered() stucks at offset where there're no ordered
extents.

Since the ordered extents are created from head to tail, we can stop the
search if there are no offset progress.

Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
Cc: <stable@vger.kernel.org> # 4.12
---
 fs/btrfs/inode.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ae4c0a1bef38..fd5934121b4b 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8309,6 +8309,7 @@ static void __endio_write_update_ordered(struct inode *inode,
 	btrfs_work_func_t func;
 	u64 ordered_offset = offset;
 	u64 ordered_bytes = bytes;
+	u64 last_offset;
 	int ret;
 
 	if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
@@ -8320,6 +8321,7 @@ static void __endio_write_update_ordered(struct inode *inode,
 	}
 
 again:
+	last_offset = ordered_offset;
 	ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,
 						   &ordered_offset,
 						   ordered_bytes,
@@ -8330,6 +8332,8 @@ static void __endio_write_update_ordered(struct inode *inode,
 	btrfs_init_work(&ordered->work, func, finish_ordered_fn, NULL, NULL);
 	btrfs_queue_work(wq, &ordered->work);
 out_test:
+	if (ordered_offset == last_offset)
+		return;
 	/*
 	 * our bio might span multiple ordered extents.  If we haven't
 	 * completed the accounting for the whole dio, go back and try again

Re: [PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[Qu Wenruo]

On 2017年09月01日 16:58, Naohiro Aota wrote:
> commit 524272607e88 ("btrfs: Handle delalloc error correctly to avoid
> ordered extent hang") introduced btrfs_cleanup_ordered_extents() to cleanup
> submitted ordered extents. However, it does not clear the ordered bit
> (Private2) of coresponding pages. Thus, the following BUG occurs from
> free_pages_check_bad() (on btrfs/125 with nospace_cache).
> 
> BUG: Bad page state in process btrfs  pfn:3fa787
> page:ffffdf2acfe9e1c0 count:0 mapcount:0 mapping:          (null) index:0xd
> flags: 0x8000000000002008(uptodate|private_2)
> raw: 8000000000002008 0000000000000000 000000000000000d 00000000ffffffff
> raw: ffffdf2acf5c1b20 ffffb443802238b0 0000000000000000 0000000000000000
> page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> bad because of flags: 0x2000(private_2)
> 
> This patch clear the flag as same as other places calling
> btrfs_dec_test_ordered_pending() for every page in the specified range.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
> Cc: <stable@vger.kernel.org> # 4.12
> ---
>   fs/btrfs/inode.c |   12 ++++++++++++
>   1 file changed, 12 insertions(+)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 24bcd5cd9cf2..ae4c0a1bef38 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -135,6 +135,18 @@ static inline void btrfs_cleanup_ordered_extents(struct inode *inode,
>   						 const u64 offset,
>   						 const u64 bytes)
>   {
> +	unsigned long index = offset >> PAGE_SHIFT;
> +	unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
> +	struct page *page;
> +
> +	while (index <= end_index) {
> +		page = find_get_page(inode->i_mapping, index);
> +		index++;
> +		if (!page)
> +			continue;
> +		ClearPagePrivate2(page);
> +		put_page(page);
> +	}

At first glance, explicitly clearing Private2 flag here seems a little 
strange to me.
However btrfs_invalidatepage() is also doing the same thing, I think 
it's fine.

Reviewed-by: Qu Wenruo <quwenruo.btrfs@gmx.com>

BTW, Private2 flag is set by extent_clear_unlock_delalloc() with 
page_ops |= PAGE_SET_PRIVATE2, but we're clearing the page flag without 
any encapsulation, it may be better to use similar function to clear 
Private2 flag.

Thanks,
Qu

>   	return __endio_write_update_ordered(inode, offset + PAGE_SIZE,
>   					    bytes - PAGE_SIZE, false);
>   }
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [PATCH 2/2] btrfs: finish ordered extent cleaning if no progress is found

[Qu Wenruo]

On 2017年09月01日 16:59, Naohiro Aota wrote:
> __endio_write_update_ordered() repeats the search until it reaches the end
> of the specified range. This works well with direct IO path, because before
> the function is called, it's ensured that there are ordered extents filling
> whole the range. It's not the case, however, when it's called from
> run_delalloc_range(): it is possible to have error in the midle of the loop
> in e.g. run_delalloc_nocow(), so that there exisits the range not covered
> by any ordered extents. By cleaning such "uncomplete" range,
> __endio_write_update_ordered() stucks at offset where there're no ordered
> extents.
> 
> Since the ordered extents are created from head to tail, we can stop the
> search if there are no offset progress.
> 
> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
> Cc: <stable@vger.kernel.org> # 4.12
> ---
>   fs/btrfs/inode.c |    4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index ae4c0a1bef38..fd5934121b4b 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -8309,6 +8309,7 @@ static void __endio_write_update_ordered(struct inode *inode,
>   	btrfs_work_func_t func;
>   	u64 ordered_offset = offset;
>   	u64 ordered_bytes = bytes;
> +	u64 last_offset;
>   	int ret;
>   
>   	if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
> @@ -8320,6 +8321,7 @@ static void __endio_write_update_ordered(struct inode *inode,
>   	}
>   
>   again:
> +	last_offset = ordered_offset;
>   	ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,
>   						   &ordered_offset,
>   						   ordered_bytes,
> @@ -8330,6 +8332,8 @@ static void __endio_write_update_ordered(struct inode *inode,
>   	btrfs_init_work(&ordered->work, func, finish_ordered_fn, NULL, NULL);
>   	btrfs_queue_work(wq, &ordered->work);
>   out_test:
> +	if (ordered_offset == last_offset)
> +		return;

Such check seems strange to me.

For ordered_offset == last_offset case, it means 
btrfs_dec_test_ordered_pending() doesn't find any ordered extent in that 
range, so we can exit.
This takes me a while to dig into btrfs_dec_test_first_ordered_pending().

Extra comment will help here, or to modify 
btrfs_dev_test_ordered_pending() to explicitly info caller there is no 
extra pending ordered extent.

Thanks,
Qu

>   	/*
>   	 * our bio might span multiple ordered extents.  If we haven't
>   	 * completed the accounting for the whole dio, go back and try again
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [PATCH 2/2] btrfs: finish ordered extent cleaning if no progress is found

[Josef Bacik]

On Fri, Sep 01, 2017 at 05:59:07PM +0900, Naohiro Aota wrote:
> __endio_write_update_ordered() repeats the search until it reaches the end
> of the specified range. This works well with direct IO path, because before
> the function is called, it's ensured that there are ordered extents filling
> whole the range. It's not the case, however, when it's called from
> run_delalloc_range(): it is possible to have error in the midle of the loop
> in e.g. run_delalloc_nocow(), so that there exisits the range not covered
> by any ordered extents. By cleaning such "uncomplete" range,
> __endio_write_update_ordered() stucks at offset where there're no ordered
> extents.
> 
> Since the ordered extents are created from head to tail, we can stop the
> search if there are no offset progress.
> 

Reviewed-by: Josef Bacik <jbacik@fb.com>

Thanks,

Josef

Re: [PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[Josef Bacik]

On Fri, Sep 01, 2017 at 05:58:47PM +0900, Naohiro Aota wrote:
> commit 524272607e88 ("btrfs: Handle delalloc error correctly to avoid
> ordered extent hang") introduced btrfs_cleanup_ordered_extents() to cleanup
> submitted ordered extents. However, it does not clear the ordered bit
> (Private2) of coresponding pages. Thus, the following BUG occurs from
> free_pages_check_bad() (on btrfs/125 with nospace_cache).
> 
> BUG: Bad page state in process btrfs  pfn:3fa787
> page:ffffdf2acfe9e1c0 count:0 mapcount:0 mapping:          (null) index:0xd
> flags: 0x8000000000002008(uptodate|private_2)
> raw: 8000000000002008 0000000000000000 000000000000000d 00000000ffffffff
> raw: ffffdf2acf5c1b20 ffffb443802238b0 0000000000000000 0000000000000000
> page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> bad because of flags: 0x2000(private_2)
> 
> This patch clear the flag as same as other places calling
> btrfs_dec_test_ordered_pending() for every page in the specified range.
> 

Reviewed-by: Josef Bacik <jbacik@fb.com>

Thanks,

Josef

Re: [PATCH 2/2] btrfs: finish ordered extent cleaning if no progress is found

[David Sterba]

On Fri, Sep 01, 2017 at 07:31:58PM +0800, Qu Wenruo wrote:
> 
> 
> On 2017年09月01日 16:59, Naohiro Aota wrote:
> > __endio_write_update_ordered() repeats the search until it reaches the end
> > of the specified range. This works well with direct IO path, because before
> > the function is called, it's ensured that there are ordered extents filling
> > whole the range. It's not the case, however, when it's called from
> > run_delalloc_range(): it is possible to have error in the midle of the loop
> > in e.g. run_delalloc_nocow(), so that there exisits the range not covered
> > by any ordered extents. By cleaning such "uncomplete" range,
> > __endio_write_update_ordered() stucks at offset where there're no ordered
> > extents.
> > 
> > Since the ordered extents are created from head to tail, we can stop the
> > search if there are no offset progress.
> > 
> > Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> > Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
> > Cc: <stable@vger.kernel.org> # 4.12
> > ---
> >   fs/btrfs/inode.c |    4 ++++
> >   1 file changed, 4 insertions(+)
> > 
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index ae4c0a1bef38..fd5934121b4b 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -8309,6 +8309,7 @@ static void __endio_write_update_ordered(struct inode *inode,
> >   	btrfs_work_func_t func;
> >   	u64 ordered_offset = offset;
> >   	u64 ordered_bytes = bytes;
> > +	u64 last_offset;
> >   	int ret;
> >   
> >   	if (btrfs_is_free_space_inode(BTRFS_I(inode))) {
> > @@ -8320,6 +8321,7 @@ static void __endio_write_update_ordered(struct inode *inode,
> >   	}
> >   
> >   again:
> > +	last_offset = ordered_offset;
> >   	ret = btrfs_dec_test_first_ordered_pending(inode, &ordered,
> >   						   &ordered_offset,
> >   						   ordered_bytes,
> > @@ -8330,6 +8332,8 @@ static void __endio_write_update_ordered(struct inode *inode,
> >   	btrfs_init_work(&ordered->work, func, finish_ordered_fn, NULL, NULL);
> >   	btrfs_queue_work(wq, &ordered->work);
> >   out_test:
> > +	if (ordered_offset == last_offset)
> > +		return;
> 
> Such check seems strange to me.
> 
> For ordered_offset == last_offset case, it means 
> btrfs_dec_test_ordered_pending() doesn't find any ordered extent in that 
> range, so we can exit.
> This takes me a while to dig into btrfs_dec_test_first_ordered_pending().
> 
> Extra comment will help here, or to modify 
> btrfs_dev_test_ordered_pending() to explicitly info caller there is no 
> extra pending ordered extent.

I'll update the patch with the comment based on your note, please send a
patch with the proposed code changes if you like.

Re: [PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[David Sterba]

On Fri, Sep 01, 2017 at 06:59:49PM +0800, Qu Wenruo wrote:
> On 2017年09月01日 16:58, Naohiro Aota wrote:
> > commit 524272607e88 ("btrfs: Handle delalloc error correctly to avoid
> > ordered extent hang") introduced btrfs_cleanup_ordered_extents() to cleanup
> > submitted ordered extents. However, it does not clear the ordered bit
> > (Private2) of coresponding pages. Thus, the following BUG occurs from
> > free_pages_check_bad() (on btrfs/125 with nospace_cache).
> > 
> > BUG: Bad page state in process btrfs  pfn:3fa787
> > page:ffffdf2acfe9e1c0 count:0 mapcount:0 mapping:          (null) index:0xd
> > flags: 0x8000000000002008(uptodate|private_2)
> > raw: 8000000000002008 0000000000000000 000000000000000d 00000000ffffffff
> > raw: ffffdf2acf5c1b20 ffffb443802238b0 0000000000000000 0000000000000000
> > page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> > bad because of flags: 0x2000(private_2)
> > 
> > This patch clear the flag as same as other places calling
> > btrfs_dec_test_ordered_pending() for every page in the specified range.
> > 
> > Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> > Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
> > Cc: <stable@vger.kernel.org> # 4.12
> > ---
> >   fs/btrfs/inode.c |   12 ++++++++++++
> >   1 file changed, 12 insertions(+)
> > 
> > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> > index 24bcd5cd9cf2..ae4c0a1bef38 100644
> > --- a/fs/btrfs/inode.c
> > +++ b/fs/btrfs/inode.c
> > @@ -135,6 +135,18 @@ static inline void btrfs_cleanup_ordered_extents(struct inode *inode,
> >   						 const u64 offset,
> >   						 const u64 bytes)
> >   {
> > +	unsigned long index = offset >> PAGE_SHIFT;
> > +	unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
> > +	struct page *page;
> > +
> > +	while (index <= end_index) {
> > +		page = find_get_page(inode->i_mapping, index);
> > +		index++;
> > +		if (!page)
> > +			continue;
> > +		ClearPagePrivate2(page);
> > +		put_page(page);
> > +	}
> 
> At first glance, explicitly clearing Private2 flag here seems a little 
> strange to me.
> However btrfs_invalidatepage() is also doing the same thing, I think 
> it's fine.
> 
> Reviewed-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
> 
> BTW, Private2 flag is set by extent_clear_unlock_delalloc() with 
> page_ops |= PAGE_SET_PRIVATE2, but we're clearing the page flag without 
> any encapsulation, it may be better to use similar function to clear 
> Private2 flag.

I agree, the Private2 flag is given another meaning in btrfs, ie. the
writeback status, so this would be better wrapped in helpers that
reflect what is the private2 flag used for. The helpers might be
trivial, but their name will be a better documentation than the random
comments that we can be found next to its use.

Re: [PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[Naohiro Aota]

On 2017年09月08日 03:25, David Sterba wrote:
> On Fri, Sep 01, 2017 at 06:59:49PM +0800, Qu Wenruo wrote:
>> On 2017年09月01日 16:58, Naohiro Aota wrote:
>>> commit 524272607e88 ("btrfs: Handle delalloc error correctly to avoid
>>> ordered extent hang") introduced btrfs_cleanup_ordered_extents() to cleanup
>>> submitted ordered extents. However, it does not clear the ordered bit
>>> (Private2) of coresponding pages. Thus, the following BUG occurs from
>>> free_pages_check_bad() (on btrfs/125 with nospace_cache).
>>>
>>> BUG: Bad page state in process btrfs  pfn:3fa787
>>> page:ffffdf2acfe9e1c0 count:0 mapcount:0 mapping:          (null) index:0xd
>>> flags: 0x8000000000002008(uptodate|private_2)
>>> raw: 8000000000002008 0000000000000000 000000000000000d 00000000ffffffff
>>> raw: ffffdf2acf5c1b20 ffffb443802238b0 0000000000000000 0000000000000000
>>> page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
>>> bad because of flags: 0x2000(private_2)
>>>
>>> This patch clear the flag as same as other places calling
>>> btrfs_dec_test_ordered_pending() for every page in the specified range.
>>>
>>> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
>>> Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
>>> Cc: <stable@vger.kernel.org> # 4.12
>>> ---
>>>   fs/btrfs/inode.c |   12 ++++++++++++
>>>   1 file changed, 12 insertions(+)
>>>
>>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
>>> index 24bcd5cd9cf2..ae4c0a1bef38 100644
>>> --- a/fs/btrfs/inode.c
>>> +++ b/fs/btrfs/inode.c
>>> @@ -135,6 +135,18 @@ static inline void btrfs_cleanup_ordered_extents(struct inode *inode,
>>>   						 const u64 offset,
>>>   						 const u64 bytes)
>>>   {
>>> +	unsigned long index = offset >> PAGE_SHIFT;
>>> +	unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
>>> +	struct page *page;
>>> +
>>> +	while (index <= end_index) {
>>> +		page = find_get_page(inode->i_mapping, index);
>>> +		index++;
>>> +		if (!page)
>>> +			continue;
>>> +		ClearPagePrivate2(page);
>>> +		put_page(page);
>>> +	}
>>
>> At first glance, explicitly clearing Private2 flag here seems a little 
>> strange to me.
>> However btrfs_invalidatepage() is also doing the same thing, I think 
>> it's fine.
>>
>> Reviewed-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
>>
>> BTW, Private2 flag is set by extent_clear_unlock_delalloc() with 
>> page_ops |= PAGE_SET_PRIVATE2, but we're clearing the page flag without 
>> any encapsulation, it may be better to use similar function to clear 
>> Private2 flag.
> 
> I agree, the Private2 flag is given another meaning in btrfs, ie. the
> writeback status, so this would be better wrapped in helpers that
> reflect what is the private2 flag used for. The helpers might be
> trivial, but their name will be a better documentation than the random
> comments that we can be found next to its use.
> 

Thanks for the reviews. I'll send a new patch to add the wrapping
function. (or should I squash the patch with this change?)

Regards,
Naohiro

Re: [PATCH 1/2] btrfs: clear ordered flag on cleaning up ordered extents

[David Sterba]

On Fri, Sep 08, 2017 at 05:10:04PM +0900, Naohiro Aota wrote:
> On 2017年09月08日 03:25, David Sterba wrote:
> > On Fri, Sep 01, 2017 at 06:59:49PM +0800, Qu Wenruo wrote:
> >> On 2017年09月01日 16:58, Naohiro Aota wrote:
> >>> commit 524272607e88 ("btrfs: Handle delalloc error correctly to avoid
> >>> ordered extent hang") introduced btrfs_cleanup_ordered_extents() to cleanup
> >>> submitted ordered extents. However, it does not clear the ordered bit
> >>> (Private2) of coresponding pages. Thus, the following BUG occurs from
> >>> free_pages_check_bad() (on btrfs/125 with nospace_cache).
> >>>
> >>> BUG: Bad page state in process btrfs  pfn:3fa787
> >>> page:ffffdf2acfe9e1c0 count:0 mapcount:0 mapping:          (null) index:0xd
> >>> flags: 0x8000000000002008(uptodate|private_2)
> >>> raw: 8000000000002008 0000000000000000 000000000000000d 00000000ffffffff
> >>> raw: ffffdf2acf5c1b20 ffffb443802238b0 0000000000000000 0000000000000000
> >>> page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
> >>> bad because of flags: 0x2000(private_2)
> >>>
> >>> This patch clear the flag as same as other places calling
> >>> btrfs_dec_test_ordered_pending() for every page in the specified range.
> >>>
> >>> Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
> >>> Fixes: 524272607e88 ("btrfs: Handle delalloc error correctly to avoid ordered extent hang")
> >>> Cc: <stable@vger.kernel.org> # 4.12
> >>> ---
> >>>   fs/btrfs/inode.c |   12 ++++++++++++
> >>>   1 file changed, 12 insertions(+)
> >>>
> >>> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> >>> index 24bcd5cd9cf2..ae4c0a1bef38 100644
> >>> --- a/fs/btrfs/inode.c
> >>> +++ b/fs/btrfs/inode.c
> >>> @@ -135,6 +135,18 @@ static inline void btrfs_cleanup_ordered_extents(struct inode *inode,
> >>>   						 const u64 offset,
> >>>   						 const u64 bytes)
> >>>   {
> >>> +	unsigned long index = offset >> PAGE_SHIFT;
> >>> +	unsigned long end_index = (offset + bytes - 1) >> PAGE_SHIFT;
> >>> +	struct page *page;
> >>> +
> >>> +	while (index <= end_index) {
> >>> +		page = find_get_page(inode->i_mapping, index);
> >>> +		index++;
> >>> +		if (!page)
> >>> +			continue;
> >>> +		ClearPagePrivate2(page);
> >>> +		put_page(page);
> >>> +	}
> >>
> >> At first glance, explicitly clearing Private2 flag here seems a little 
> >> strange to me.
> >> However btrfs_invalidatepage() is also doing the same thing, I think 
> >> it's fine.
> >>
> >> Reviewed-by: Qu Wenruo <quwenruo.btrfs@gmx.com>
> >>
> >> BTW, Private2 flag is set by extent_clear_unlock_delalloc() with 
> >> page_ops |= PAGE_SET_PRIVATE2, but we're clearing the page flag without 
> >> any encapsulation, it may be better to use similar function to clear 
> >> Private2 flag.
> > 
> > I agree, the Private2 flag is given another meaning in btrfs, ie. the
> > writeback status, so this would be better wrapped in helpers that
> > reflect what is the private2 flag used for. The helpers might be
> > trivial, but their name will be a better documentation than the random
> > comments that we can be found next to its use.
> > 
> 
> Thanks for the reviews. I'll send a new patch to add the wrapping
> function. (or should I squash the patch with this change?)

Please send a separate patch.