Re: [PATCH v3 0/3] data integrity: Stabilize pages during writeback for ext4

Excerpts from Christoph Hellwig's message of 2011-05-04 14:46:44 -0400:

This seems to miss out on a lot of the generic functionality like
write_cache_pages and block_page_mkwrite and just patch it into
the ext4 copy & paste variants.  Please make sure your patches also
work for filesystem that use more of the generic functionality like
xfs or ext2 (the latter one might be fun for the mmap case).

Probably after the block_commit_write in block_page_mkwrite()
Another question is, do we want to introduce a wait_on_stable_page_writeback()?

This would allow us to add a check against the bdi requesting stable
pages.

Also what's the status of btrfs?  I remembered there was one or two
bits missing despite doing the right thing in most areas.

As far as I know btrfs is getting it right.  The only bit missing is the
one Nick Piggin pointed out where it is possible to change mmap'd O_DIRECT
memory in flight while a DIO is in progress.  Josef has a test case that
demonstrates this.

Nick had a plan to fix it, but it involved redoing the get_user_pages
api.

-chris

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