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From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <quwenruo@cn.fujitsu.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2 07/11] btrfs: Add noinode_cache mount option.
Date: Fri, 3 Jan 2014 18:52:44 +0100	[thread overview]
Message-ID: <20140103175244.GR6498@twin.jikos.cz> (raw)
In-Reply-To: <1388729434-19799-8-git-send-email-quwenruo@cn.fujitsu.com>

On Fri, Jan 03, 2014 at 02:10:30PM +0800, Qu Wenruo wrote:
> Add noinode_cache mount option to disable inode map cache with
> remount option.

This looks almost safe, there's a sync_filesystem called before the
filesystem's remount handler, the transaction gets committed and flushes
all tha data related to inode_cache.

The caching thread keeps running, which is not a serious problem as
it'll finish at umount time, only consuming resources.

There's a window between sync_filesystem and successful remount when the
INODE_MAP_CACHE bit is set and the cache could be used to get a free ino,
then the INODE_MAP_CACHE is cleared but the ino cache remains is not
synced back to disk, normally called from transaction commit via
btrfs_unpin_free_ino. I haven't looked if something else blocks that to
happen.

I'd leave this patch out for now, it probably needs more code updates
than just unsetting the bit.

david

  reply	other threads:[~2014-01-03 17:52 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-03  6:10 [PATCH v2 00/11] btrfs: Add missing pairing mount options Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 01/11] btrfs: Add "barrier" option to support "-o remount,barrier" Qu Wenruo
2014-01-03  8:44   ` Mike Fleetwood
2014-01-03  9:20     ` Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 02/11] btrfs: Add noautodefrag mount option Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 03/11] btrfs: Add nocheck_int " Qu Wenruo
2014-01-03 17:13   ` David Sterba
2014-01-06  0:51     ` Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 04/11] btrfs: Add nodiscard " Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 05/11] btrfs: Add noenospc_debug " Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 06/11] btrfs: Add noflushoncommit " Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 07/11] btrfs: Add noinode_cache " Qu Wenruo
2014-01-03 17:52   ` David Sterba [this message]
2014-01-06  0:54     ` Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 08/11] btrfs: Add acl " Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 09/11] btrfs: Add datacow " Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 10/11] btrfs: Add datasum " Qu Wenruo
2014-01-03  6:10 ` [PATCH v2 11/11] btrfs: Add treelog " Qu Wenruo
2014-01-03 17:52 ` [PATCH v2 00/11] btrfs: Add missing pairing mount options Eric Sandeen
2014-01-06  0:58   ` Qu Wenruo
2014-01-03 17:58 ` David Sterba
2014-01-06  1:01   ` Qu Wenruo

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