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Date: Thu, 22 Jun 2017 11:52:36 -0400
From: "Theodore Ts'o" <tytso@mit.edu>
To: Tahsin Erdogan <tahsin@google.com>
Cc: Andreas Dilger <adilger@dilger.ca>,
        "Darrick J . Wong" <darrick.wong@oracle.com>, Jan Kara <jack@suse.cz>,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 30/32] ext4: eliminate xattr entry e_hash recalculation
 for removes
Message-ID: <20170622155236.ncjwgdhlhwd5mssg@thunk.org>
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        Tahsin Erdogan <tahsin@google.com>,
        Andreas Dilger <adilger@dilger.ca>,
        "Darrick J . Wong" <darrick.wong@oracle.com>,
        Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20170622014939.3592-1-tahsin@google.com>
 <20170622014939.3592-7-tahsin@google.com>
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On Wed, Jun 21, 2017 at 06:49:37PM -0700, Tahsin Erdogan wrote:
> When an extended attribute block is modified, ext4_xattr_hash_entry()
> recalculates e_hash for the entry that is pointed by s->here. This is
> unnecessary if the modification is to remove an entry.
> 
> Currently, if the removed entry is the last one and there are other
> entries remaining, hash calculation targets the just erased entry which
> has been filled with zeroes and effectively does nothing. If the removed
> entry is not the last one and there are more entries, this time it will
> recalculate hash on the next entry which is totally unnecessary.
> 
> Fix these by moving the decision on when to recalculate hash to
> ext4_xattr_set_entry().
> 
> Signed-off-by: Tahsin Erdogan <tahsin@google.com>

Thanks, applied.

					- Ted