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From: Al Viro <viro@zeniv.linux.org.uk>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: linux-fsdevel@vger.kernel.org, linux-mtd@lists.infradead.org,
	Jan Kara <jack@suse.com>, Richard Weinberger <richard@nod.at>,
	kernel@pengutronix.de
Subject: Re: [PATCH 04/11] fs, quota: introduce wait_super_thawed() to wait until a superblock is thawed
Date: Thu, 15 Aug 2019 00:35:56 +0100	[thread overview]
Message-ID: <20190814233556.GV1131@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190814121834.13983-5-s.hauer@pengutronix.de>

On Wed, Aug 14, 2019 at 02:18:27PM +0200, Sascha Hauer wrote:
> quota uses three different functions to get a superblock from a
> block_device. Instead, retrieve the superblock always with get_super()
> and introduce wait_super_thawed() which is then used to wait until the
> superblock is thawed. This way the code can better be shared with the
> code introduced in the next step: We want to add quota support for
> filesystems without a block_device, so here functions around a
> block_device can't be used.

> + *	wait_super_thawed - wait for a superblock being thawed
> + *	@sb: superblock to wait for
> + *	@excl: if true, get s_umount semaphore exclusively
> + *
> + * Wait until the superblock is thawed. s_umount semaphore must be released on
> + * entry and will be held when returning.
> + */

Never expose anything like that - if locking rules depend upon the flags,
it MUST NOT be anything beyond a static helper.  I'm serious - that kind
of stuff ends up with trouble again and again.  Just don't.

WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@zeniv.linux.org.uk>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: linux-fsdevel@vger.kernel.org,
	Richard Weinberger <richard@nod.at>,
	linux-mtd@lists.infradead.org, kernel@pengutronix.de,
	Jan Kara <jack@suse.com>
Subject: Re: [PATCH 04/11] fs, quota: introduce wait_super_thawed() to wait until a superblock is thawed
Date: Thu, 15 Aug 2019 00:35:56 +0100	[thread overview]
Message-ID: <20190814233556.GV1131@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190814121834.13983-5-s.hauer@pengutronix.de>

On Wed, Aug 14, 2019 at 02:18:27PM +0200, Sascha Hauer wrote:
> quota uses three different functions to get a superblock from a
> block_device. Instead, retrieve the superblock always with get_super()
> and introduce wait_super_thawed() which is then used to wait until the
> superblock is thawed. This way the code can better be shared with the
> code introduced in the next step: We want to add quota support for
> filesystems without a block_device, so here functions around a
> block_device can't be used.

> + *	wait_super_thawed - wait for a superblock being thawed
> + *	@sb: superblock to wait for
> + *	@excl: if true, get s_umount semaphore exclusively
> + *
> + * Wait until the superblock is thawed. s_umount semaphore must be released on
> + * entry and will be held when returning.
> + */

Never expose anything like that - if locking rules depend upon the flags,
it MUST NOT be anything beyond a static helper.  I'm serious - that kind
of stuff ends up with trouble again and again.  Just don't.

______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

  reply	other threads:[~2019-08-14 23:35 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14 12:18 [PATCH 00/11] Add quota support to UBIFS Sascha Hauer
2019-08-14 12:18 ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 01/11] quota: Make inode optional Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 02/11] quota: Only module_put the format when existing Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-15 11:18   ` Jan Kara
2019-08-15 11:18     ` Jan Kara
2019-08-16 11:49     ` Sascha Hauer
2019-08-16 11:49       ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 03/11] fs: move __get_super() out of loop Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 23:32   ` Al Viro
2019-08-14 23:32     ` Al Viro
2019-08-14 12:18 ` [PATCH 04/11] fs, quota: introduce wait_super_thawed() to wait until a superblock is thawed Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 23:35   ` Al Viro [this message]
2019-08-14 23:35     ` Al Viro
2019-08-14 12:18 ` [PATCH 05/11] quota: Allow to pass quotactl a mountpoint Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 22:42   ` kbuild test robot
2019-08-14 22:42     ` kbuild test robot
2019-08-14 23:33   ` kbuild test robot
2019-08-14 23:33     ` kbuild test robot
2019-08-14 23:36   ` Al Viro
2019-08-14 23:36     ` Al Viro
2019-08-14 23:39     ` Al Viro
2019-08-14 23:39       ` Al Viro
2019-08-14 23:51       ` Al Viro
2019-08-14 23:51         ` Al Viro
2019-08-15  9:53         ` Jan Kara
2019-08-15  9:53           ` Jan Kara
2019-08-15  7:46       ` Sascha Hauer
2019-08-15  7:46         ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 06/11] ubifs: move checks and preparation into setflags() Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 07/11] ubifs: Add support for FS_IOC_FS[SG]ETXATTR ioctls Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 14:11   ` Mainz, Roland
2019-08-14 14:11     ` Mainz, Roland
2019-08-15  7:31     ` Sascha Hauer
2019-08-15  7:31       ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 08/11] ubifs: do not ubifs_inode() on potentially NULL pointer Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 09/11] ubifs: Add support for project id Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 10/11] ubifs: export get_znode Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-14 12:18 ` [PATCH 11/11] ubifs: Add quota support Sascha Hauer
2019-08-14 12:18   ` Sascha Hauer
2019-08-15 11:17   ` Jan Kara
2019-08-15 11:17     ` Jan Kara

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