linux-kernel - Re: [PATCH v3 1/5] btrfs: replace stripe extents

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Date: Tue, 2 Jul 2024 05:41:19 +0000
From: Johannes Thumshirn <Johannes.Thumshirn@....com>
To: Josef Bacik <josef@...icpanda.com>, Johannes Thumshirn <jth@...nel.org>
CC: Chris Mason <clm@...com>, David Sterba <dsterba@...e.com>,
	"linux-btrfs@...r.kernel.org" <linux-btrfs@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/5] btrfs: replace stripe extents

On 01.07.24 22:37, Josef Bacik wrote:
>> +	if (ret == -EEXIST)
>> +		ret = replace_raid_extent_item(trans, &stripe_key,
>> +					       stripe_extent, item_size);
> 
> I had another thought, how often is this particular thing happening?  Bec ause
> we're doing 3 path allocations here in the worst case.  If it happens more than
> say 10% of the time then we need to allocate a path once in
> btrfs_insert_one_raid_extent(), do the insert, and if it fails re-use that path
> to do the delete and insert the new one.  Thanks,

That indeed is a good question. I'll add some tracepoints to see how 
often this is getting called.