On Wed, 2 Oct 2013, J. Bruce Fields wrote:
> On Wed, Oct 02, 2013 at 11:47:22AM -0700, Sage Weil wrote:
> > On Wed, 2 Oct 2013, J. Bruce Fields wrote:
> > > On Wed, Oct 02, 2013 at 09:05:27AM -0700, Christoph Hellwig wrote:
> > > > On Wed, Oct 02, 2013 at 10:25:27AM -0400, J. Bruce Fields wrote:
> > > > > If so then it's no huge code duplication to it by hand:
> > > > >
> > > > > if (inode->i_op->getattr)
> > > > > inode->i_op->getattr(path->mnt, path->dentry, &stat);
> > > > > else
> > > > > generic_fillattr(inode, &stat);
> > > >
> > > > Maybe make that a vfs_getattr_nosec and let vfs_getattr call it?
> > > >
> > > > Including a proper kerneldoc comment explaining when to use it, please.
> > >
> > > Something like this?
> >
> > I'm late to this thread, but: getattr() is a comparatively expensive
> > operation for just getting an (immutable) ino value on a distributed or
> > clustered fs. It would be nice if there were a separate call that didn't
> > try to populate all the other kstat fields with valid data. Something
> > like this was part of the xstat series from forever ago (a bit mask passed
> > to getattr indicating which fields were needed), so the approach below
> > might be okay if we think we'll get there sometime soon, but my preference
> > would be for another fix...
>
> Understood, and perhaps this code should eventually take advantage of
> xstat, but:
>
> - this code isn't handling the common case, so we're not too
> worried about the performance, and
> - you also have the option of defining your own
> export_operations->get_name. Especially consider that if you
> have some better way to answer the question "what is the name
> of inode X in directory Y" that's better than reading Y
> looking for a matching inode number.
Ah, I see. Sounds good then!
Thanks-
sage
>
> --b.
>
> > (Ceph also uses 64-bit inos.)
> >
> > Thanks!
> > sage
> >
> >
> > >
> > > --b.
> > >
> > > commit 8418a41b7192cf2f372ae091207adb29a088f9a0
> > > Author: J. Bruce Fields <bfields@xxxxxxxxxx>
> > > Date: Tue Sep 10 11:41:12 2013 -0400
> > >
> > > exportfs: fix 32-bit nfsd handling of 64-bit inode numbers
> > >
> > > Symptoms were spurious -ENOENTs on stat of an NFS filesystem from a
> > > 32-bit NFS server exporting a very large XFS filesystem, when the
> > > server's cache is cold (so the inodes in question are not in cache).
> > >
> > > Reported-by: Trevor Cordes <trevor@xxxxxxxxxxxxx>
> > > Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> > >
> > > diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c
> > > index 293bc2e..811831a 100644
> > > --- a/fs/exportfs/expfs.c
> > > +++ b/fs/exportfs/expfs.c
> > > @@ -215,7 +215,7 @@ struct getdents_callback {
> > > struct dir_context ctx;
> > > char *name; /* name that was found. It already points to a
> > > buffer NAME_MAX+1 is size */
> > > - unsigned long ino; /* the inum we are looking for */
> > > + u64 ino; /* the inum we are looking for */
> > > int found; /* inode matched? */
> > > int sequence; /* sequence counter */
> > > };
> > > @@ -255,10 +255,10 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
> > > struct inode *dir = path->dentry->d_inode;
> > > int error;
> > > struct file *file;
> > > + struct kstat stat;
> > > struct getdents_callback buffer = {
> > > .ctx.actor = filldir_one,
> > > .name = name,
> > > - .ino = child->d_inode->i_ino
> > > };
> > >
> > > error = -ENOTDIR;
> > > @@ -268,6 +268,16 @@ static int get_name(const struct path *path, char *name, struct dentry *child)
> > > if (!dir->i_fop)
> > > goto out;
> > > /*
> > > + * inode->i_ino is unsigned long, kstat->ino is u64, so the
> > > + * former would be insufficient on 32-bit hosts when the
> > > + * filesystem supports 64-bit inode numbers. So we need to
> > > + * actually call ->getattr, not just read i_ino:
> > > + */
> > > + error = vfs_getattr_nosec(path, &stat);
> > > + if (error)
> > > + return error;
> > > + buffer.ino = stat.ino;
> > > + /*
> > > * Open the directory ...
> > > */
> > > file = dentry_open(path, O_RDONLY, cred);
> > > diff --git a/fs/stat.c b/fs/stat.c
> > > index 04ce1ac..71a39e8 100644
> > > --- a/fs/stat.c
> > > +++ b/fs/stat.c
> > > @@ -37,14 +37,21 @@ void generic_fillattr(struct inode *inode, struct kstat *stat)
> > >
> > > EXPORT_SYMBOL(generic_fillattr);
> > >
> > > -int vfs_getattr(struct path *path, struct kstat *stat)
> > > +/**
> > > + * vfs_getattr_nosec - getattr without security checks
> > > + * @path: file to get attributes from
> > > + * @stat: structure to return attributes in
> > > + *
> > > + * Get attributes without calling security_inode_getattr.
> > > + *
> > > + * Currently the only caller other than vfs_getattr is internal to the
> > > + * filehandle lookup code, which uses only the inode number and returns
> > > + * no attributes to any user. Any other code probably wants
> > > + * vfs_getattr.
> > > + */
> > > +int vfs_getattr_nosec(struct path *path, struct kstat *stat)
> > > {
> > > struct inode *inode = path->dentry->d_inode;
> > > - int retval;
> > > -
> > > - retval = security_inode_getattr(path->mnt, path->dentry);
> > > - if (retval)
> > > - return retval;
> > >
> > > if (inode->i_op->getattr)
> > > return inode->i_op->getattr(path->mnt, path->dentry, stat);
> > > @@ -53,6 +60,18 @@ int vfs_getattr(struct path *path, struct kstat *stat)
> > > return 0;
> > > }
> > >
> > > +EXPORT_SYMBOL_GPL(vfs_getattr_nosec);
> > > +
> > > +int vfs_getattr(struct path *path, struct kstat *stat)
> > > +{
> > > + int retval;
> > > +
> > > + retval = security_inode_getattr(path->mnt, path->dentry);
> > > + if (retval)
> > > + return retval;
> > > + return vfs_getattr_nosec(path, stat);
> > > +}
> > > +
> > > EXPORT_SYMBOL(vfs_getattr);
> > >
> > > int vfs_fstat(unsigned int fd, struct kstat *stat)
> > > diff --git a/include/linux/fs.h b/include/linux/fs.h
> > > index 9818747..5a51faa 100644
> > > --- a/include/linux/fs.h
> > > +++ b/include/linux/fs.h
> > > @@ -2500,6 +2500,7 @@ extern int page_symlink(struct inode *inode, const char *symname, int len);
> > > extern const struct inode_operations page_symlink_inode_operations;
> > > extern int generic_readlink(struct dentry *, char __user *, int);
> > > extern void generic_fillattr(struct inode *, struct kstat *);
> > > +int vfs_getattr_nosec(struct path *path, struct kstat *stat);
> > > extern int vfs_getattr(struct path *, struct kstat *);
> > > void __inode_add_bytes(struct inode *inode, loff_t bytes);
> > > void inode_add_bytes(struct inode *inode, loff_t bytes);
> > > --
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>
>
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