Re: [PATCH 3/3 v2] dax: use pfn_mkwrite to update c/mtime + freeze protection

[Boaz Harrosh <boaz@plexistor.com>]

On 03/05/2015 11:24 AM, Boaz Harrosh wrote:
> 
> [v1]
> Without this patch, c/mtime is not updated correctly when mmap'ed page is
> first read from and then written to.
> 
> A new xfstest is submitted for testing this (generic/080)
> 
> [v2]
> Jan Kara has pointed out that if we add the
> sb_start/end_pagefault pair in the new pfn_mkwrite we
> are then fixing another bug where: A user could start
> writing to the page while filesystem is frozen.
> 

Thanks Jan.

Just as curiosity, does the freezing code goes and turns all mappings
into read-only, Also for pfn mapping?

Do you think there is already an xfstest freezing test that should now
fail, and will succeed after this patch (v2). Something like:
  * mmap-read/write before the freeze
  * freeze the fs
  * Another thread tries to mmap-write, should get stuck
  * unfreeze the fs
  * Now mmap-writer continues

Thanks again
Boaz

> CC: Jan Kara <jack@suse.cz>
> Signed-off-by: Yigal Korman <yigal@plexistor.com>
> Signed-off-by: Boaz Harrosh <boaz@plexistor.com>
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