fuse: nfs export special lookups
Implement the get_parent export operation by sending a LOOKUP request with
".." as the name.
Implement looking up an inode by node ID after it has been evicted from
the cache. This is done by seding a LOOKUP request with "." as the name
(for all file types, not just directories).
The filesystem can set the FUSE_EXPORT_SUPPORT flag in the INIT reply, to
indicate that it supports these special lookups.
Thanks to John Muir for the original implementation of this feature.
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Cc: Matthew Wilcox <matthew@wil.cx>
Cc: David Teigland <teigland@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 5d3146d..3a87607 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -363,6 +363,9 @@
/** Do not send separate SETATTR request before open(O_TRUNC) */
unsigned atomic_o_trunc : 1;
+ /** Filesystem supports NFS exporting. Only set in INIT */
+ unsigned export_support : 1;
+
/*
* The following bitfields are only for optimization purposes
* and hence races in setting them will not cause malfunction
@@ -473,6 +476,9 @@
int generation, struct fuse_attr *attr,
u64 attr_valid, u64 attr_version);
+int fuse_lookup_name(struct super_block *sb, u64 nodeid, struct qstr *name,
+ struct fuse_entry_out *outarg, struct inode **inode);
+
/**
* Send FORGET command
*/
diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 71fa76a..7d2f7d6 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -562,6 +562,7 @@
static struct dentry *fuse_get_dentry(struct super_block *sb,
struct fuse_inode_handle *handle)
{
+ struct fuse_conn *fc = get_fuse_conn_super(sb);
struct inode *inode;
struct dentry *entry;
int err = -ESTALE;
@@ -570,8 +571,27 @@
goto out_err;
inode = ilookup5(sb, handle->nodeid, fuse_inode_eq, &handle->nodeid);
- if (!inode)
- goto out_err;
+ if (!inode) {
+ struct fuse_entry_out outarg;
+ struct qstr name;
+
+ if (!fc->export_support)
+ goto out_err;
+
+ name.len = 1;
+ name.name = ".";
+ err = fuse_lookup_name(sb, handle->nodeid, &name, &outarg,
+ &inode);
+ if (err && err != -ENOENT)
+ goto out_err;
+ if (err || !inode) {
+ err = -ESTALE;
+ goto out_err;
+ }
+ err = -EIO;
+ if (get_node_id(inode) != handle->nodeid)
+ goto out_iput;
+ }
err = -ESTALE;
if (inode->i_generation != handle->generation)
goto out_iput;
@@ -659,11 +679,46 @@
return fuse_get_dentry(sb, &parent);
}
+static struct dentry *fuse_get_parent(struct dentry *child)
+{
+ struct inode *child_inode = child->d_inode;
+ struct fuse_conn *fc = get_fuse_conn(child_inode);
+ struct inode *inode;
+ struct dentry *parent;
+ struct fuse_entry_out outarg;
+ struct qstr name;
+ int err;
+
+ if (!fc->export_support)
+ return ERR_PTR(-ESTALE);
+
+ name.len = 2;
+ name.name = "..";
+ err = fuse_lookup_name(child_inode->i_sb, get_node_id(child_inode),
+ &name, &outarg, &inode);
+ if (err && err != -ENOENT)
+ return ERR_PTR(err);
+ if (err || !inode)
+ return ERR_PTR(-ESTALE);
+
+ parent = d_alloc_anon(inode);
+ if (!parent) {
+ iput(inode);
+ return ERR_PTR(-ENOMEM);
+ }
+ if (get_node_id(inode) != FUSE_ROOT_ID) {
+ parent->d_op = &fuse_dentry_operations;
+ fuse_invalidate_entry_cache(parent);
+ }
+
+ return parent;
+}
static const struct export_operations fuse_export_operations = {
.fh_to_dentry = fuse_fh_to_dentry,
.fh_to_parent = fuse_fh_to_parent,
.encode_fh = fuse_encode_fh,
+ .get_parent = fuse_get_parent,
};
static const struct super_operations fuse_super_operations = {
@@ -695,6 +750,11 @@
fc->no_lock = 1;
if (arg->flags & FUSE_ATOMIC_O_TRUNC)
fc->atomic_o_trunc = 1;
+ if (arg->minor >= 9) {
+ /* LOOKUP has dependency on proto version */
+ if (arg->flags & FUSE_EXPORT_SUPPORT)
+ fc->export_support = 1;
+ }
if (arg->flags & FUSE_BIG_WRITES)
fc->big_writes = 1;
} else {
@@ -721,7 +781,7 @@
arg->minor = FUSE_KERNEL_MINOR_VERSION;
arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
- FUSE_BIG_WRITES;
+ FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES;
req->in.h.opcode = FUSE_INIT;
req->in.numargs = 1;
req->in.args[0].size = sizeof(*arg);
diff --git a/include/linux/fuse.h b/include/linux/fuse.h
index d482821..265635d 100644
--- a/include/linux/fuse.h
+++ b/include/linux/fuse.h
@@ -104,11 +104,14 @@
/**
* INIT request/reply flags
+ *
+ * FUSE_EXPORT_SUPPORT: filesystem handles lookups of "." and ".."
*/
#define FUSE_ASYNC_READ (1 << 0)
#define FUSE_POSIX_LOCKS (1 << 1)
#define FUSE_FILE_OPS (1 << 2)
#define FUSE_ATOMIC_O_TRUNC (1 << 3)
+#define FUSE_EXPORT_SUPPORT (1 << 4)
#define FUSE_BIG_WRITES (1 << 5)
/**
