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From: "Li, Hao" <lihao2018.fnst@cn.fujitsu.com>
To: "linux-xfs@vger.kernel.org" <linux-xfs@vger.kernel.org>,
	"linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org>
Cc: "ira.weiny@intel.com" <ira.weiny@intel.com>,
	"Gotou, Yasunori" <y-goto@fujitsu.com>
Subject: Can we change the S_DAX flag immediately on XFS without dropping caches?
Date: Tue, 28 Jul 2020 02:00:08 +0000	[thread overview]
Message-ID: <9dc179147f6a47279d801445f3efeecc@G08CNEXMBPEKD04.g08.fujitsu.local> (raw)

Hi,

I have noticed that we have to drop caches to make the changing of S_DAX
flag take effect after using chattr +x to turn on DAX for a existing
regular file. The related function is xfs_diflags_to_iflags, whose
second parameter determines whether we should set S_DAX immediately.

I can't figure out why we do this. Is this because the page caches in
address_space->i_pages are hard to deal with? I also wonder what will
happen if we set S_DAX unconditionally. Thanks!

Regards,
Hao Li



             reply	other threads:[~2020-07-28  2:00 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-28  2:00 Li, Hao [this message]
2020-07-28  2:20 ` Can we change the S_DAX flag immediately on XFS without dropping caches? Dave Chinner
2020-07-29  2:23   ` Yasunori Goto
2020-07-29 16:10     ` Ira Weiny
2020-07-31  9:12       ` Li, Hao
2020-08-05  8:10         ` Li, Hao
2020-08-05 15:44           ` Darrick J. Wong
2020-08-07 16:57             ` Ira Weiny
2020-07-31 10:04       ` Yasunori Goto
2020-07-29 23:21     ` Dave Chinner
2020-07-31  9:15       ` Li, Hao
2020-07-31  9:59       ` Yasunori Goto
2020-08-07 17:09         ` Ira Weiny
2020-08-18  9:16           ` Li, Hao

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