From: "Rafael J. Wysocki" <rafael@kernel.org>
To: "Luis R. Rodriguez" <mcgrof@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
bart.vanassche@wdc.com, ming.lei@redhat.com,
"Ted Ts'o" <tytso@mit.edu>,
"Darrick J. Wong" <darrick.wong@oracle.com>,
Jiri Kosina <jikos@kernel.org>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Pavel Machek <pavel@ucw.cz>, Len Brown <len.brown@intel.com>,
linux-fsdevel@vger.kernel.org,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
Todd Brandt <todd.e.brandt@linux.intel.com>,
nborisov@suse.com, Jan Kara <jack@suse.cz>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Oliver Neukum <ONeukum@suse.com>,
oleksandr@natalenko.name,
Oleg Antonyan <oleg.b.antonyan@gmail.com>,
Yu Chen <yu.chen.surf@gmail.com>,
Dan Williams <dan.j.williams@intel.com>,
Linux PM <linux-pm@vger.kernel.org>,
linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 05/11] fs: add iterate_supers_excl() and iterate_supers_reverse_excl()
Date: Thu, 30 Nov 2017 00:48:15 +0100 [thread overview]
Message-ID: <CAJZ5v0gO49=pXGEdi42Hka=Rf=SqVWp-QSJf9_+bGuOgsHMFig@mail.gmail.com> (raw)
In-Reply-To: <20171129232356.28296-6-mcgrof@kernel.org>
On Thu, Nov 30, 2017 at 12:23 AM, Luis R. Rodriguez <mcgrof@kernel.org> wrote:
> There are use cases where we wish to traverse the superblock list
> but also capture errors, and in which case we want to avoid having
> our callers issue a lock themselves since we can do the locking for
> the callers. Provide a iterate_supers_excl() which calls a function
> with the write lock held. If an error occurs we capture it and
> propagate it.
>
> Likewise there are use cases where we wish to traverse the superblock
> list but in reverse order. The new iterate_supers_reverse_excl() helpers
> does this but also also captures any errors encountered.
>
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
> fs/super.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 2 ++
> 2 files changed, 93 insertions(+)
>
> diff --git a/fs/super.c b/fs/super.c
> index a63513d187e8..885711c1d35b 100644
> --- a/fs/super.c
> +++ b/fs/super.c
> @@ -605,6 +605,97 @@ void iterate_supers(void (*f)(struct super_block *, void *), void *arg)
> spin_unlock(&sb_lock);
> }
>
> +/**
> + * iterate_supers_excl - exclusively call func for all active superblocks
> + * @f: function to call
> + * @arg: argument to pass to it
> + *
> + * Scans the superblock list and calls given function, passing it
> + * locked superblock and given argument. Returns 0 unless an error
> + * occurred on calling the function on any superblock.
> + */
> +int iterate_supers_excl(int (*f)(struct super_block *, void *), void *arg)
> +{
> + struct super_block *sb, *p = NULL;
> + int error = 0;
> +
> + spin_lock(&sb_lock);
> + list_for_each_entry(sb, &super_blocks, s_list) {
> + if (hlist_unhashed(&sb->s_instances))
> + continue;
> + sb->s_count++;
> + spin_unlock(&sb_lock);
Can anything bad happen if the list is modified at this point by a
concurrent thread?
> +
> + down_write(&sb->s_umount);
> + if (sb->s_root && (sb->s_flags & SB_BORN)) {
> + error = f(sb, arg);
> + if (error) {
> + up_write(&sb->s_umount);
> + spin_lock(&sb_lock);
> + __put_super(sb);
> + break;
> + }
> + }
> + up_write(&sb->s_umount);
> +
> + spin_lock(&sb_lock);
> + if (p)
> + __put_super(p);
> + p = sb;
> + }
> + if (p)
> + __put_super(p);
> + spin_unlock(&sb_lock);
> +
> + return error;
> +}
> +
next prev parent reply other threads:[~2017-11-29 23:48 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-29 23:23 [PATCH 00/11] fs: use freeze_fs on suspend/hibernate Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 01/11] fs: provide unlocked helper for freeze_super() Luis R. Rodriguez
2017-11-30 16:58 ` Jan Kara
2017-11-29 23:23 ` [PATCH 02/11] fs: provide unlocked helper thaw_super() Luis R. Rodriguez
2017-11-30 16:59 ` Jan Kara
2017-11-29 23:23 ` [PATCH 03/11] fs: add frozen sb state helpers Luis R. Rodriguez
2017-11-30 17:13 ` Jan Kara
2017-11-30 19:05 ` Luis R. Rodriguez
2017-12-01 11:47 ` Jan Kara
2017-12-01 21:13 ` Luis R. Rodriguez
2017-12-21 11:03 ` Jan Kara
2018-04-18 0:59 ` Luis R. Rodriguez
2018-04-18 10:12 ` Jan Kara
2018-04-20 18:49 ` Luis R. Rodriguez
2018-04-21 23:53 ` Jan Kara
2018-04-22 1:22 ` Luis R. Rodriguez
2018-04-22 2:53 ` Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 04/11] fs: distinguish between user initiated freeze and kernel initiated freeze Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 05/11] fs: add iterate_supers_excl() and iterate_supers_reverse_excl() Luis R. Rodriguez
2017-11-29 23:48 ` Rafael J. Wysocki [this message]
2017-11-30 0:22 ` Luis R. Rodriguez
2017-11-30 1:34 ` Dave Chinner
2017-11-30 1:40 ` Rafael J. Wysocki
2017-11-30 16:57 ` Jan Kara
2017-11-29 23:23 ` [PATCH 06/11] fs: freeze on suspend and thaw on resume Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 07/11] xfs: remove not needed freezing calls Luis R. Rodriguez
2017-11-30 16:21 ` Jan Kara
2017-11-30 20:32 ` Rafael J. Wysocki
2017-11-30 23:30 ` Dave Chinner
2017-11-30 23:40 ` Rafael J. Wysocki
2017-11-29 23:23 ` [PATCH 08/11] ext4: " Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 09/11] f2fs: " Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 10/11] nilfs2: " Luis R. Rodriguez
2017-11-29 23:23 ` [PATCH 11/11] jfs: " Luis R. Rodriguez
2017-11-30 16:36 ` [PATCH 00/11] fs: use freeze_fs on suspend/hibernate Yu Chen
2017-11-30 16:41 ` Jiri Kosina
2017-11-30 16:50 ` Yu Chen
2017-12-01 19:05 ` Jeff Layton
2017-12-01 21:51 ` Dave Chinner
2017-11-30 17:01 ` Bart Van Assche
2017-11-30 19:42 ` Luis R. Rodriguez
2017-11-30 20:53 ` Bart Van Assche
2017-11-30 21:03 ` Dave Chinner
2017-11-30 21:51 ` Pavel Machek
2017-12-01 0:44 ` Luis R. Rodriguez
2017-12-13 1:09 ` Rafael J. Wysocki
2017-12-19 16:50 ` Luis R. Rodriguez
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