that space for extended attributes should be preallocated, instead of
using a sparse attribute file. NOTE: This can result in a really
large file full of zeros. However, it can prevent a low disk condition
from causing an attribute write to fail, which is good for security and
consistency attributes.
o Unlink the attribute file during initattr if an error occurs -- this is
alright, as we specify O_CREAT when opening the file.
attributes (recently committed). Using extattrctl, the extended attribute
service may be started and stopped for specific file systems; specific
attributes may be enabled or disabled, and the backing file for each
attribute configured. Also, backing files may be initialized.
Reviewed by: adrian, bp, freebsd-fs, the unthanked masses
Obtained from: TrustedBSD
