From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 364058F77; Tue, 6 Aug 2024 18:51:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722970299; cv=none; b=SJasnmLFE+LXX6ueNo9YP6WHnjRLwyL0I1/tv/ueyec5Yu87uxdSL3T/3HNu+QfbXxLNNloJ5XyWFH3dk2oxcSxdod3cmY/OwVvPtMZ6KerimgDtrLvAInnI2Ipi9mZ8H6VBb4YmcNDU2vrSCWZhK0DTU9klH4D2ROG9YiAVtBU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722970299; c=relaxed/simple; bh=yriVAzItDrt9m0IOacwV5U8YZFGUHYkZLyfOw6hqRvQ=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=OTIH99PXsnmhohOXJs3HrlAQ+xPhTKXwg72vhTsk+Zqmq4oRUAzvFxGG7G4Kv8YBFYSEa1hHH0536RY097iC6kNTYKojSe0UaAGyKCQihlIe1tBI3kiNdqsL3hfbxMc1bZ6jN+Tjv9Qusx2TlyUzDqVGcQIuD4vF3tqQ5elgHPQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=J5uvVOex; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="J5uvVOex" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B308AC32786; Tue, 6 Aug 2024 18:51:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1722970298; bh=yriVAzItDrt9m0IOacwV5U8YZFGUHYkZLyfOw6hqRvQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=J5uvVOexNdVv7IR46Jfa9rqBmRSdna/6vLRIrZySt3iFaWKCQgdi/W4yqml3d5xDY C/JaQ3bDBNNLyp0VKyYKaABFahYaonWSCeABssEXElKjSP0V/O8gR3JKMIBdn3cYpy L1Ue4JD1bbwIESFe/uQQCJyk/M7dKsFur892xBg084SM5/LR3nU+oIhw/ff66GoiG5 wIE08ra124LN4rZ6nlVHv2QChyzggumcOPno70X1w3LzZ+Cyr5V1+vcjP9pz/gplBL R8Lj+Iycq7bJejOtgmkEh7K/jGIfgnwHS+dIfoqAQhMK3ZAiDLh5rHDZNlWfdgGVPD zRP2pvZNjdy6A== Date: Tue, 6 Aug 2024 11:51:38 -0700 From: "Darrick J. Wong" To: John Garry Cc: chandan.babu@oracle.com, dchinner@redhat.com, hch@lst.de, viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, linux-xfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, catherine.hoang@oracle.com, martin.petersen@oracle.com Subject: Re: [PATCH v3 01/14] xfs: only allow minlen allocations when near ENOSPC Message-ID: <20240806185138.GF623936@frogsfrogsfrogs> References: <20240801163057.3981192-1-john.g.garry@oracle.com> <20240801163057.3981192-2-john.g.garry@oracle.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240801163057.3981192-2-john.g.garry@oracle.com> On Thu, Aug 01, 2024 at 04:30:44PM +0000, John Garry wrote: > From: Dave Chinner > > When we are near ENOSPC and don't have enough free > space for an args->maxlen allocation, xfs_alloc_space_available() > will trim args->maxlen to equal the available space. However, this > function has only checked that there is enough contiguous free space > for an aligned args->minlen allocation to succeed. Hence there is no > guarantee that an args->maxlen allocation will succeed, nor that the > available space will allow for correct alignment of an args->maxlen > allocation. > > Further, by trimming args->maxlen arbitrarily, it breaks an > assumption made in xfs_alloc_fix_len() that if the caller wants > aligned allocation, then args->maxlen will be set to an aligned > value. It then skips the tail alignment and so we end up with > extents that aren't aligned to extent size hint boundaries as we > approach ENOSPC. > > To avoid this problem, don't reduce args->maxlen by some random, > arbitrary amount. If args->maxlen is too large for the available > space, reduce the allocation to a minlen allocation as we know we > have contiguous free space available for this to succeed and always > be correctly aligned. > > Signed-off-by: Dave Chinner > Signed-off-by: John Garry > --- > fs/xfs/libxfs/xfs_alloc.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > index 59326f84f6a5..d559d992c6ef 100644 > --- a/fs/xfs/libxfs/xfs_alloc.c > +++ b/fs/xfs/libxfs/xfs_alloc.c > @@ -2524,14 +2524,23 @@ xfs_alloc_space_available( > if (available < (int)max(args->total, alloc_len)) > return false; > > + if (flags & XFS_ALLOC_FLAG_CHECK) > + return true; > + > /* > - * Clamp maxlen to the amount of free space available for the actual > - * extent allocation. > + * If we can't do a maxlen allocation, then we must reduce the size of > + * the allocation to match the available free space. We know how big > + * the largest contiguous free space we can allocate is, so that's our > + * upper bound. However, we don't exaclty know what alignment/size > + * constraints have been placed on the allocation, so we can't > + * arbitrarily select some new max size. Hence make this a minlen > + * allocation as we know that will definitely succeed and match the > + * callers alignment constraints. > */ > - if (available < (int)args->maxlen && !(flags & XFS_ALLOC_FLAG_CHECK)) { > - args->maxlen = available; > + alloc_len = args->maxlen + (args->alignment - 1) + args->minalignslop; > + if (longest < alloc_len) { > + args->maxlen = args->minlen; Same question as the June 21st posting: Is it possible to reduce maxlen the largest multiple of the alignment that is still less than @longest? --D > ASSERT(args->maxlen > 0); > - ASSERT(args->maxlen >= args->minlen); > } > > return true; > -- > 2.31.1 > >