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: Fri, 30 Jul 2021 15:57:49 +0200 From: Mikhail Morfikov <mmorfikov@...il.com> To: Theodore Ts'o <tytso@....edu> Cc: linux-ext4@...r.kernel.org Subject: Re: Is it safe to use the bigalloc feature in the case of ext4 filesystem? I have a question concerning the *hugefiles* parameters. When a filesystems is created using the hugefiles stanza, it also creates lots of chunk-* files inside of the /storage/ dir. You say that it guarantees the huge files to be 100% contiguous. But if I create the filesystem with the preallocated files that consume the whole drive, how am I suppose to use that drive? :) Are the files only temporary, and should they be removed once the filesystem is "ready"? What's the purpose of such options? Do they affect the EXT4 metadata in some way? I mean, what's the change compared to not using the options? Also I have a question concerning the hugefiles stanza itself -- it's missing the bigalloc feature, should it be there? On 29/07/2021 19.59, Theodore Ts'o wrote: >... > If you see the hugefile and hugefiles stanzas below, that's an example > of one way bigalloc has gotten a fair amount of use. In this use case > mke2fs has pre-allocated the huge data files guaranteeing that they > will be 100% contiguous. We're using a 32k cluster becuase there are > some metadata files where better allocation efficiencies is desired. > >... > > hugefiles = { > features = extent,huge_file,flex_bg,uninit_bg,dir_nlink,extra_isize,^resize_inode,sparse_super2 > hash_alg = half_md4 > reserved_ratio = 0.0 > num_backup_sb = 0 > packed_meta_blocks = 1 > make_hugefiles = 1 > inode_ratio = 4194304 > hugefiles_dir = /storage > hugefiles_name = chunk- > hugefiles_digits = 5 > hugefiles_size = 4G > hugefiles_align = 256M > hugefiles_align_disk = true > zero_hugefiles = false > flex_bg_size = 262144 > } > > hugefile = { > features = extent,huge_file,bigalloc,flex_bg,uninit_bg,dir_nlink,extra_isize,^resize_inode,sparse_super2 > cluster_size = 32768 > hash_alg = half_md4 > reserved_ratio = 0.0 > num_backup_sb = 0 > packed_meta_blocks = 1 > make_hugefiles = 1 > inode_ratio = 4194304 > hugefiles_dir = /storage > hugefiles_name = huge-file > hugefiles_digits = 0 > hugefiles_size = 0 > hugefiles_align = 256M > hugefiles_align_disk = true > num_hugefiles = 1 > zero_hugefiles = false > }
Powered by blists - more mailing lists