From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: [PATCH/RFC] fscache/cachefiles versus btrfs Date: Mon, 20 Apr 2015 14:49:56 +1000 Message-ID: <20150420144956.1f489f67@notabene.brown> References: <20150409174916.5a2efef5@notabene.brown> <29536.1428571388@warthog.procyon.org.uk> <20150410112431.0e9c337d@notabene.brown> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; boundary="Sig_/dVcelSonvmDGq0X=lchLGNa"; protocol="application/pgp-signature" Cc: linux-btrfs@vger.kernel.org, linux-cachefs@redhat.com, linux-fsdevel@vger.kernel.org To: David Howells Return-path: In-Reply-To: <20150410112431.0e9c337d@notabene.brown> Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org --Sig_/dVcelSonvmDGq0X=lchLGNa Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Fri, 10 Apr 2015 11:24:31 +1000 NeilBrown wrote: > On Thu, 09 Apr 2015 10:23:08 +0100 David Howells wr= ote: >=20 > > NeilBrown wrote: > >=20 > > > Is there a better way? Could a better way be created? Maybe > > > SEEK_DATA_RELIABLE ?? > >=20 > > fiemap() maybe? > >=20 > > > Also, if you do try to use fscache on btrfs with 3.19, then nothing g= ets > > > cached (as expected) and with a heavy load you can lose a race and ge= t an > > > asserting fail in fscache_enqueue_operation > >=20 > > Do you have the patches here applied? > >=20 > > http://git.kernel.org/cgit/linux/kernel/git/dhowells/linux-fs.git/log/= ?h=3Dfscache-fixes > >=20 >=20 > Do I don't. I had looked through them and while they did seem to be > addressing similar sorts of races, nothing seems like an obvious match. > I haven't been able to reproduce the BUG_ON myself. I only have a report > of it repeatedly affecting someone else: >=20 > https://bugzilla.opensuse.org/show_bug.cgi?id=3D908706 >=20 > I'll probably have to be happy with fixing usage on btrfs, and hope the o= ther > bug is fixed already or doesn't become a problem. I managed to reproduce the bug, and when I applied your patches I cannot any more. So it looks like you've fixed it - thanks. That just leave the bmap issue. I'll post a patch which causes lseek to be used when the fs says that is OK. Thanks, NeilBrown --Sig_/dVcelSonvmDGq0X=lchLGNa Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIVAwUBVTSFdDnsnt1WYoG5AQKb9Q//ZDSe96Txtf7d6U5S89kGEclwSZHtCass 5WNCDawzeqMObZHDn4/jw0geTRj4NE6tpY74PcpPGAQdCzzy9sEC75+69mVCKgP/ WvVaH8KBXcWh8X2W1hHzMVsVq8us2J1aP1gS6LvJsBx33ajBZFitCkSIw4QK5jTz krpIqrYHxtHshIRqHrv/0bZDcUT/uks6MnIIL7q+g92mBBdJC3xFrlQ+LbgJATdO VT6TLbuneHPBZ2CdfZS7LaLbSv9XhgPHg7P7qZqN50ruEmASKdtay35B1aRee+Pz 00lemeByskVhRTN5zlebRRk187HNm/y073gAcn7ZhfqbMdo0SvJ4n5YEEg17a1bw RPClMZW7GpMBFyA3IYUhxipJr4hHNN5vpPJuq47oyZMTFMNpu/8VHIpin3Ow7bJE VMrixSz/G4BGR7g9c80JB2VRNzk9+gJR3rXgtBxgEaJLnGNvpHf3ocHIjW5Y4Bpk CCjdz8MuNn3fY3b6jjrp87ENRfLjci7bEAAEAIOdgPdLSS7W/E+3qN9Xn+ja7Ubh /vvQfscwMAHDciJTy2cmfZjARWACKBkbLov+f3q9uH0BNxG8mA1dRqNg3wVwrR2o PB4j3Rd5dVw7kuncySOkPoUKQwtzoViW5Coeu6fmgD7+wreJuTIalGO2mjRFQUjz P9+DooGLVfE= =KOPe -----END PGP SIGNATURE----- --Sig_/dVcelSonvmDGq0X=lchLGNa--