On 19-Oct-09, at 16:24, Steve French wrote:
On Mon, Oct 19, 2009 at 3:11 PM, Andreas Dilger <adilger@xxxxxxx>
wrote:
On 19-Oct-09, at 13:45, Steve French wrote:
Yes - the fake xattr approach was the approach that I preferred
(since I could do this trivially to cifs, and for ext4 it seems
equally
easy),
but I wonder if this "path based" approach is slightly harder for
Samba,
since for most cases Samba maps to "handle based" equivalents
(when the same operation can come in eitherpath based or
handle based - Samba mostly maps to handle based).
Could you please elaborate what you mean by "path based" for xattrs?
They can be gotten with sys_fgetxattr() from a file handle just as
easily as from the filename.
Although handle based interfaces are there for xattrs in userspace,
internally the xattr calls are path based, so handle based
calls get converted to path based in kernel and you could lose
some of the performance benefit - path based could be slightly
slower (due to path revalidation, and access checks) than
handle based calls.
int (*setxattr) (struct dentry *, const char *,const void
*,size_t,int);
ssize_t (*getxattr) (struct dentry *, const char *, void *,
size_t);
ssize_t (*listxattr) (struct dentry *, char *, size_t);
int (*removexattr) (struct dentry *, const char *);
I'm not sure I understand your point. sys_fgetxattr() maps directly to
vfs_getxattr(), and while it still does permission checks, that doesn't
have anything to do with pathname revalidation AFAICS.
There are an equal number of permission checks in sys_fstat-
>vfs_getattr()
as in sys_fgetxattr->vfs_getxattr().
As for being able to write to the "create time" attribute, I would
prefer
that this be a filesystem mount option. For some users (myself
included)
I don't care whether Windows is unhappy that it can't update this
creation
time - I'd prefer to know when a file is actually created.
I agree - if create time could be overwritten - that behavior hould be
configurable (another post mentioned the alternative to mount
option - a flag for this perhaps along the lines of the a "backup
intent"
flag - although somewhat different than what Windows uses that for).
If this is a flag that a user can configure/select themselves, then it
is completely useless to me. If it is a mount option and/or possibly an
additional process capability that would be more useful.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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