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Re: [PATCH 03/10] xfs: allow assigning the tail lsn with the AIL lock he

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 03/10] xfs: allow assigning the tail lsn with the AIL lock held
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Tue, 27 Mar 2012 13:18:20 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120327164644.597749707@xxxxxxxxxxxxxxxxxxxxxx>
References: <20120327164400.967415009@xxxxxxxxxxxxxxxxxxxxxx> <20120327164644.597749707@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 03/27/12 11:44, Christoph Hellwig wrote:
Provide a variant of xlog_assign_tail_lsn that has the AIL lock already
held.  By doing so we do an additional atomic_read + atomic_set under
the lock, which comes down to two instructions.

Switch xfs_trans_ail_update_bulk and xfs_trans_ail_delete_bulk to the
new version to reduce the number of lock roundtrips, and prepare for
a new addition that would require a third lock roundtrip in
xfs_trans_ail_delete_bulk.  This addition is also the reason for
slightly rearranging the conditionals and relying on xfs_log_space_wake
for checking that the filesystem has been shut down internally.

Signed-off-by: Christoph Hellwig<hch@xxxxxx>


Looks good.

Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>

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