From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeff Mahoney Subject: Re: NOCOW + compress-force = bug Date: Tue, 13 Mar 2012 14:11:05 -0400 Message-ID: <4F5F8DB9.40208@suse.de> References: <4F38B8F0.5020506@yahoo.com> <4F38BE53.4080204@parallels.com> <20120213141040.GG15350@twin.jikos.cz> <20120216195515.643f4aa7@natsu> <20120216175815.GM21896@shiny> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 To: Chris Mason , Roman Mamedov , dave@jikos.cz, dima , linux-btrfs@vger.kernel.org Return-path: In-Reply-To: <20120216175815.GM21896@shiny> List-ID: -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 02/16/2012 12:58 PM, Chris Mason wrote: > On Thu, Feb 16, 2012 at 07:55:15PM +0600, Roman Mamedov wrote: >> Hello, >> >> Please be aware that there seems to be a possible problem with >> using NOCOW flag on files situated on a filesystem mounted with >> compress-force(=lzo, in my case). >> >> Since experimenting with NOCOW, I started regularly hitting this >> BUG at extent-tree.c:5813 >> >> 5813 BUG_ON(!(flags & >> BTRFS_BLOCK_FLAG_FULL_BACKREF)); >> >> I was unable to make netconsole work over a bridged interface, so >> can only post screenshots of this OOPS: >> http://romanrm.ru/pics/2012/2012-02-16-btrfs-bug-1.jpg >> http://romanrm.ru/pics/2012/2012-02-16-btrfs-bug-2.jpg >> >> This happened four times already, and always on snapshot creation >> (but not every case). I have hourly snapshots in crontab, and >> only one case out of about ten fails with this problem. Did not >> try to deliberately reproduce it yet by manually making snapshots >> very often, etc. > > Interesting, NOCOW and compression don't really mix. We always cow > for compression. I'll try to reproduce it. I hit this one today without nocow or compression. The only thing non-default was that I mounted with -ossd. The backing store was a 1GB non-sparse loopback file on tmpfs. I had kdump enabled and with 16GB, I wasn't waiting around for the dump to complete. If it happens again, I'll have a full stack trace. My test case was filling the disk while making snapshots. - -Jeff - -- Jeff Mahoney SUSE Labs -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQIcBAEBAgAGBQJPX424AAoJEB57S2MheeWybq0P/1xv09dKpBfuvK/2vpyriebN 3RsPtHVZgAL9y9XeLVw0KPlRKTGM+PIyc+AEloIiYQgULifA625nPa6+DXlNqzCp 0jKVleAE5RLCOtBDC91GX8JO/55fszjTQHSXAHjSRr4vr/4bZEf4tLBTwbW7Nfax YAUPQ6cu+FQlCDWppXMLswKmLsmnewTnKrZp0YQTOTVGY3dajsvGTR3vR0VyxMwY FZ13hvGOfP+UXsZC1qijxA3g8CrWwu/dhiU/dnCYwhcCF+0ONiHHHhB3krDAkNP8 yVAZgoSGJsIUdDiqeKXaSm8RDT6vGQwnJicFQSkUqGiHXyi+/fXVUULNSbgj39EC R2jHLlXtMMaRyoqiM/wOfZUOr5MGQhk0duXB1NjNGAaffAsjvBY0c8y4yvGJVhtR E2EknQLHr2jBWF8KCpLe0YYLPjcB3Gp3SPUhyGZbg4ATUAv2amMcw13deI8I17gI v9dJSCWyi+r5c0d26rgtsS9SpfM8qHz5A/EvqVtn99DgS+O49o4+3F8M+2WioDjM mHndWGXqg4fBIwrpxvo5RtBmQ8OYgZzxZXoZU3XP/eRS4c6z8OJ9U92/pUFP64Id 6tpqU1E9XxEijTWwcIyvkSzu6bjOLQucePBPCKkWLtTy9XrbNMTmvcGozKNCTVKK km1EWb9RM2m8JPrEc+JA =ywbL -----END PGP SIGNATURE-----