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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: Miao Xie <miaoxie@huawei.com>,
	linux-btrfs@vger.kernel.org,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCH RESEND v4 6/8] vfs: Add get_vfsmount_sb() function to get vfsmount from a given sb.
Date: Fri, 30 Jan 2015 02:14:45 +0000	[thread overview]
Message-ID: <20150130021445.GH29656@ZenIV.linux.org.uk> (raw)
In-Reply-To: <54CAE1E3.1040406@cn.fujitsu.com>

On Fri, Jan 30, 2015 at 09:44:03AM +0800, Qu Wenruo wrote:

> This shouldn't happen. If someone is ro, the whole fs should be ro, right?

Wrong.  Individual vfsmounts over an r/w superblock might very well be r/o.
As for that trylock...  What for?  It invites transient failures for no
good reason.  Removal of sysfs entry will block while write(2) to that sucker
is in progress, so btrfs shutdown will block at that point in ctree_close().
It won't go away under you.

Now, you might want to move those sysfs entry removals to the very beginning
of btrfs_kill_super(), but that's a different story - you need only to make
sure that they are removed not later than the destruction of the data
structures they need (IOW, the current location might very well be OK - I
hadn't checked the details).

As for "it won't go r/o under us" - sb_want_write() will do that just fine.

  parent reply	other threads:[~2015-01-30  2:14 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-29  2:24 [PATCH RESEND v4 0/8] Fix freeze/sysfs deadlock in better method Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 1/8] Revert "btrfs: add support for processing pending changes" related commits Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 2/8] btrfs: Make btrfs_parse_options() parse mount option in a atomic way Qu Wenruo
2015-01-30  0:31   ` Miao Xie
2015-01-30  1:20     ` Qu Wenruo
2015-01-30  1:29       ` Miao Xie
2015-01-30  1:33         ` Qu Wenruo
2015-01-30  2:06           ` Miao Xie
2015-01-30  2:51             ` Qu Wenruo
2015-01-30  3:21               ` Miao Xie
2015-01-30  3:25                 ` Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 3/8] btrfs: Introduce per-transaction mount_opt to keep mount option consistent during transaction Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 4/8] btrfs: Use btrfs_test_trans_opt() to handle SPACE_CACHE if it's under transaction protect Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 5/8] btrfs: Use btrfs_test_trans_opt() to handle INODE_CACHE " Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 6/8] vfs: Add get_vfsmount_sb() function to get vfsmount from a given sb Qu Wenruo
2015-01-29 12:37   ` David Sterba
2015-01-29 15:23     ` Al Viro
2015-01-30  1:11       ` Qu Wenruo
2015-01-30  1:11         ` Qu Wenruo
2015-01-30  2:09         ` Al Viro
2015-01-30  2:20           ` Qu Wenruo
2015-01-30  2:20             ` Qu Wenruo
2015-01-30  0:52   ` Miao Xie
2015-01-30  1:44     ` Qu Wenruo
2015-01-30  1:44       ` Qu Wenruo
2015-01-30  2:02       ` Qu Wenruo
2015-01-30  2:02         ` Qu Wenruo
2015-01-30  3:22         ` Miao Xie
2015-01-30  3:22           ` Miao Xie
2015-01-30  3:30           ` Qu Wenruo
2015-01-30  3:30             ` Qu Wenruo
2015-01-30  2:14       ` Al Viro [this message]
2015-01-30  4:14         ` Miao Xie
2015-01-30  4:37           ` Al Viro
2015-01-30  5:34             ` Miao Xie
2015-01-30  6:15               ` Al Viro
2015-01-30  5:30           ` Qu Wenruo
2015-01-30  5:30             ` Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 7/8] btrfs: Use mnt_want_write() to protect label change Qu Wenruo
2015-01-29  2:24 ` [PATCH RESEND v4 8/8] btrfs: Use mnt_want_write() to protect sysfs feature change Qu Wenruo

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