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SubjectRe: [PATCH 4.9 089/116] btrfs: flush write bio if we loop in extent_write_cache_pages
On Thu, Feb 13, 2020 at 10:01:09PM +0100, David Sterba wrote:
>On Thu, Feb 13, 2020 at 07:20:33AM -0800, Greg Kroah-Hartman wrote:
>> From: Josef Bacik <josef@toxicpanda.com>
>>
>> [ Upstream commit 96bf313ecb33567af4cb53928b0c951254a02759 ]
>
>This commit does not exist in my tree, the correct upstream commit of
>the backported patch should be 42ffb0bf584ae5b6b38f72259af1e0ee417ac77f.
>
>> --- a/fs/btrfs/extent_io.c
>> +++ b/fs/btrfs/extent_io.c
>> @@ -4060,6 +4060,14 @@ static int extent_write_cache_pages(struct extent_io_tree *tree,
>> */
>> scanned = 1;
>> index = 0;
>> +
>> + /*
>> + * If we're looping we could run into a page that is locked by a
>> + * writer and that writer could be waiting on writeback for a
>> + * page in our current bio, and thus deadlock, so flush the
>> + * write bio here.
>> + */
>> + flush_write_bio(data);
>
>This has been modified to apply, flush_write_bio does not return a value
>in 4.9, perhaps this led to the different commit id.

Ah yes. This patch was tricky because there were two "big" things that
broke on the backport:

1. flush_write_bio() returning a value.
2. The 'data' -> 'epd' rename.

96bf313ecb3 comes from when both of the above conditions overlapped, and
I forgot that I'm basing my second backport change on something that was
already modified.

--
Thanks,
Sasha

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