lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Wed, 15 Jan 2020 14:31:01 +0100 From: Christoph Hellwig <hch@....de> To: Qu Wenruo <quwenruo.btrfs@....com> Cc: Andreas Dilger <adilger@...ger.ca>, David Howells <dhowells@...hat.com>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, Al Viro <viro@...iv.linux.org.uk>, Christoph Hellwig <hch@....de>, "Theodore Y. Ts'o" <tytso@....edu>, "Darrick J. Wong" <darrick.wong@...cle.com>, Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>, David Sterba <dsterba@...e.com>, linux-ext4 <linux-ext4@...r.kernel.org>, linux-xfs <linux-xfs@...r.kernel.org>, linux-btrfs <linux-btrfs@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org> Subject: Re: Problems with determining data presence by examining extents? On Wed, Jan 15, 2020 at 09:10:44PM +0800, Qu Wenruo wrote: > > That allows userspace to distinguish fe_physical addresses that may be > > on different devices. This isn't in the kernel yet, since it is mostly > > useful only for Btrfs and nobody has implemented it there. I can give > > you details if working on this for Btrfs is of interest to you. > > IMHO it's not good enough. > > The concern is, one extent can exist on multiple devices (mirrors for > RAID1/RAID10/RAID1C2/RAID1C3, or stripes for RAID5/6). > I didn't see how it can be easily implemented even with extra fields. > > And even we implement it, it can be too complex or bug prune to fill > per-device info. It's also completely bogus for the use cases to start with. fiemap is a debug tool reporting the file system layout. Using it for anything related to actual data storage and data integrity is a receipe for disaster. As said the right thing for the use case would be something like the NFS READ_PLUS operation. If we can't get that easily it can be emulated using lseek SEEK_DATA / SEEK_HOLE assuming no other thread could be writing to the file, or the raciness doesn't matter.
Powered by blists - more mailing lists