[PATCH 20/27] afs: Detect cell aliases 3 - YFS Cells with a canonical cell name op

David Howells
2020-05-29T22:02:41Z

YFS Volume Location servers have an operation by which the cell name may be
queried. Use this to find out what a YFS server thinks the canonical cell
name should be.

Signed-off-by: David Howells <dhowells@redhat.com>
---

fs/afs/vl_alias.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++
fs/afs/vl_rotate.c | 4 +++
2 files changed, 64 insertions(+)

diff --git a/fs/afs/vl_alias.c b/fs/afs/vl_alias.c
index 76bfa4dde4a4..1fcb63c65ba9 100644
--- a/fs/afs/vl_alias.c
+++ b/fs/afs/vl_alias.c
@@ -268,12 +268,72 @@ static int afs_query_for_alias(struct afs_cell *cell, struct key *key)
return 1;
}

+/*
+ * Look up a VLDB record for a volume.
+ */
+static char *afs_vl_get_cell_name(struct afs_cell *cell, struct key *key)
+{
+ struct afs_vl_cursor vc;
+ char *cell_name = ERR_PTR(-EDESTADDRREQ);
+ bool skipped = false, not_skipped = false;
+ int ret;
+
+ if (!afs_begin_vlserver_operation(&vc, cell, key))
+ return ERR_PTR(-ERESTARTSYS);
+
+ while (afs_select_vlserver(&vc)) {
+ if (!test_bit(AFS_VLSERVER_FL_IS_YFS, &vc.server->flags)) {
+ vc.ac.error = -EOPNOTSUPP;
+ skipped = true;
+ continue;
+ }
+ not_skipped = true;
+ cell_name = afs_yfsvl_get_cell_name(&vc);
+ }
+
+ ret = afs_end_vlserver_operation(&vc);
+ if (skipped && !not_skipped)
+ ret = -EOPNOTSUPP;
+ return ret < 0 ? ERR_PTR(ret) : cell_name;
+}
+
+static int yfs_check_canonical_cell_name(struct afs_cell *cell, struct key *key)
+{
+ struct afs_cell *master;
+ char *cell_name;
+
+ cell_name = afs_vl_get_cell_name(cell, key);
+ if (IS_ERR(cell_name))
+ return PTR_ERR(cell_name);
+
+ if (strcmp(cell_name, cell->name) == 0) {
+ kfree(cell_name);
+ return 0;
+ }
+
+ master = afs_lookup_cell(cell->net, cell_name, strlen(cell_name),
+ NULL, false);
+ kfree(cell_name);
+ if (IS_ERR(master)) {
+ kfree(cell_name);
+ return PTR_ERR(master);
+ }
+
+ cell->alias_of = master; /* Transfer our ref */
+ return 1;
+}
+
static int afs_do_cell_detect_alias(struct afs_cell *cell, struct key *key)
{
struct afs_volume *root_volume;
+ int ret;

_enter("%s", cell->name);

+ ret = yfs_check_canonical_cell_name(cell, key);
+ if (ret != -EOPNOTSUPP)
+ return ret;
+
/* Try and get the root.cell volume for comparison with other cells */
root_volume = afs_sample_volume(cell, key, "root.cell", 9);
if (!IS_ERR(root_volume)) {
diff --git a/fs/afs/vl_rotate.c b/fs/afs/vl_rotate.c
index 72eacc14e6e1..f405ca8b240a 100644
--- a/fs/afs/vl_rotate.c
+++ b/fs/afs/vl_rotate.c
@@ -151,6 +151,10 @@ bool afs_select_vlserver(struct afs_vl_cursor *vc)
vc->error = error;
vc->flags |= AFS_VL_CURSOR_RETRY;
goto next_server;
+
+ case -EOPNOTSUPP:
+ _debug("notsupp");
+ goto next_server;
}