[PATCH v5 05/31] block-backend: special comments for blk_set/get_perm due to fuse

[Emanuele Giuseppe Esposito <eesposit@redhat.com>]

Fuse logic can be classified as I/O, so there is no BQL held
during its execution. And yet, it uses blk_{get/set}_perm
functions, that are classified as BQL and clearly require
the BQL lock. Since there is no easy solution for this,
add a couple of TODOs and FIXME in the relevant sections of the
code.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
 block/block-backend.c | 10 ++++++++++
 block/export/fuse.c   | 16 ++++++++++++++--
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/block/block-backend.c b/block/block-backend.c
index 1f0bda578e..7a4b50a8f0 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -888,6 +888,11 @@ int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm,
                  Error **errp)
 {
     int ret;
+    /*
+     * FIXME: blk_{get/set}_perm should be always called under
+     * BQL, but it is not the case right now (see block/export/fuse.c)
+     */
+    /* assert(qemu_in_main_thread()); */
 
     if (blk->root && !blk->disable_perm) {
         ret = bdrv_child_try_set_perm(blk->root, perm, shared_perm, errp);
@@ -904,6 +909,11 @@ int blk_set_perm(BlockBackend *blk, uint64_t perm, uint64_t shared_perm,
 
 void blk_get_perm(BlockBackend *blk, uint64_t *perm, uint64_t *shared_perm)
 {
+    /*
+     * FIXME: blk_{get/set}_perm should be always called under
+     * BQL, but it is not the case right now (see block/export/fuse.c)
+     */
+    /* assert(qemu_in_main_thread()); */
     *perm = blk->perm;
     *shared_perm = blk->shared_perm;
 }
diff --git a/block/export/fuse.c b/block/export/fuse.c
index 823c126d23..7ceb8d783b 100644
--- a/block/export/fuse.c
+++ b/block/export/fuse.c
@@ -89,7 +89,10 @@ static int fuse_export_create(BlockExport *blk_exp,
     /* For growable exports, take the RESIZE permission */
     if (args->growable) {
         uint64_t blk_perm, blk_shared_perm;
-
+        /*
+         * FIXME: blk_{get/set}_perm should not be here, as permissions
+         * should be modified only under BQL and here we are not!
+         */
         blk_get_perm(exp->common.blk, &blk_perm, &blk_shared_perm);
 
         ret = blk_set_perm(exp->common.blk, blk_perm | BLK_PERM_RESIZE,
@@ -400,6 +403,11 @@ static int fuse_do_truncate(const FuseExport *exp, int64_t size,
 
     /* Growable exports have a permanent RESIZE permission */
     if (!exp->growable) {
+
+        /*
+         * FIXME: blk_{get/set}_perm should not be here, as permissions
+         * should be modified only under BQL and here we are not!
+         */
         blk_get_perm(exp->common.blk, &blk_perm, &blk_shared_perm);
 
         ret = blk_set_perm(exp->common.blk, blk_perm | BLK_PERM_RESIZE,
@@ -413,7 +421,11 @@ static int fuse_do_truncate(const FuseExport *exp, int64_t size,
                        truncate_flags, NULL);
 
     if (!exp->growable) {
-        /* Must succeed, because we are only giving up the RESIZE permission */
+        /*
+         * Must succeed, because we are only giving up the RESIZE permission.
+         * FIXME: blk_{get/set}_perm should not be here, as permissions
+         * should be modified only under BQL and here we are not!
+         */
         blk_set_perm(exp->common.blk, blk_perm, blk_shared_perm, &error_abort);
     }
 
-- 
2.27.0