From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: [PATCH] DM RAID: Add ability to restore transiently failed devices on resume Date: Mon, 22 Apr 2013 10:43:26 +1000 Message-ID: <20130422104326.217ef2f8@notabene.brown> References: <1365712023.9799.1.camel@f16> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=PGP-SHA1; boundary="Sig_/REDHpfAjuTkhkmIr.ust_K0"; protocol="application/pgp-signature" Return-path: In-Reply-To: <1365712023.9799.1.camel@f16> Sender: linux-raid-owner@vger.kernel.org To: Jonathan Brassow Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids --Sig_/REDHpfAjuTkhkmIr.ust_K0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Thu, 11 Apr 2013 15:27:03 -0500 Jonathan Brassow wrote: > DM RAID: Add ability to restore transiently failed devices on resume >=20 > This patch adds code to the resume function to check over the devices > in the RAID array. If any are found to be marked as failed and their > superblocks can be read, an attempt is made to reintegrate them into > the array. This allows the user to refresh the array with a simple > suspend and resume of the array - rather than having to load a > completely new table, allocate and initialize all the structures and > throw away the old instantiation. >=20 > Signed-off-by: Jonathan Brassow Is this really a good idea? =20 Just because you can read the superblock, that doesn't mean you can read any other block in the array. If the auto-recovery were optional I might consider it, but having it be enforced on every suspend/resume just doesn't seem safe to me. Have I misunderstood? Is this that hard to achieve in user-space? > + if (test_bit(Faulty, &r->flags) && r->sb_page && > + !read_disk_sb(r, r->sb_size)) { I know it is fairly widely used, especially for 'strcmp', but I absolutely despise this construct. !read_disk_sb() sound like "not read_disk_sb" or "could not read the disk's superblock" but it actually means "did not fail to read the disk's superblock" - the exact reverse. If 0 means success, I like to see an explicit test for 0: read_disk_sb() =3D=3D 0 NeilBrown --Sig_/REDHpfAjuTkhkmIr.ust_K0 Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.19 (GNU/Linux) iQIVAwUBUXSHrjnsnt1WYoG5AQLZDg/+N4bj3VC7NMEhMIStXHheFWRkTEuD+Q/x zezzE5QLIIXJWqd4bnkjIqUx/lNpCnQGHjAD+bidySBwmuLOtEitt1kH05tnnmlE qTu8o+UF4A4uajWkpGqObQq4Pi3g+SJb1L5OriVKOGYxBvABT/owEh59l9qjNMo1 01E5JyhuO8nsu57vBFaX7wF8sAlxYtygOS7lEHJuDvkvSK0qbk8pvSH52fhaHCyS uETgpBmO6PZ7BCrKqEJNwfpxW8GG9MRnh9UEX8cRtreSQYnCy+euk14cryIC934j 0SOEUdBuRGkPZ4a0XEaTY7/xWLV55HQKUIz1V2QXfz654wQnIOMg8WCb2Mvm+2VN J+tb8OsqqS7qW2tXA7Adih36GCdLzwIGFdIcNr2UyaqCDMYnkdiMlYPCDAZI/xkD upLb2hAduVhfKzcGgR+GMMCe7NyHMplNj2QTthXwDqiBadwZ3ixx8UO4Q/f74/Mu pcqPnu4GAmZPT/PyzaiGnxKldkQfrO4MuUCWDJ3SxvNw8YLZy/lqLXFKs4kf/n4T zGBz1x9HoPTiCzjlP9aU80wVxPBUQwN7OKcrjgwFi6/qgjkhG6FbpneZST1qTKpg rwU63DVIsSNMLgeQGd3DJsJs8rkvH8dRYgbY0eTjvL+Yum+MxviYVJ51LfOlDwZB kYxTGbzmoS0= =udcb -----END PGP SIGNATURE----- --Sig_/REDHpfAjuTkhkmIr.ust_K0--