Re: [rfc] new stat*fs-like syscall?

[Brad Boyer]

On Sat, Jun 26, 2010 at 09:54:44PM +0900, J. R. Okajima wrote:
> Christoph Hellwig:
> > That's really job for a pathconf system call that allows quering random
> > paramters.
> 
> Do you mean it should be implemented such like this?
> vfs_pathconf(struct dentry, int parm)
> --> return d_sb->s_op->pathconf(parm)

I would suggest making it an inode operation if we do actually add it. Most
cases are going to be per super-block, but it might be easier to transparently
handle things like _PC_PIPE_BUF in glibc if it could call an fpathconf type
system call on the pipe fd. I haven't looked at the current glibc code for
that particular selector. The only one I looked at in any detail was
_PC_LINK_MAX, which is the one you already discussed and is obviously a
per-sb option. The only drawback I can see is that making it an inode
operation would make the vfs_pathconf fail on a negative dentry, but that
seems like a very strange thing to support in any case.

> I am afraid it is overdesign because the actual parameter(for FS) is
> _PC_LINK_MAX only. All other params are already handled by VFS, glibc or
> sb->statfs.

	Brad Boyer
	flar@xxxxxxxxxxxxx

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