dax: Use radix tree entry lock to protect cow faults

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When doing cow faults, we cannot directly fill in PTE as we do for other
faults as we rely on generic code to do proper accounting of the cowed page.
We also have no page to lock to protect against races with truncate as
other faults have and we need the protection to extend until the moment
generic code inserts cowed page into PTE thus at that point we have no
protection of fs-specific i_mmap_sem. So far we relied on using
i_mmap_lock for the protection however that is completely special to cow
faults. To make fault locking more uniform use DAX entry lock instead.

Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>

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Jan Kara 2016-05-12 18:29:19 +02:00 • committed by Ross Zwisler

parent ac401cc782

commit bc2466e425

4 changed files with 37 additions and 27 deletions

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7

include/linux/dax.h

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7

include/linux/mm.h

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