dm verity: conditionally enable branching for "try_verify_in_tasklet"

Use jump_label to limit the need for branching unless the optional
"try_verify_in_tasklet" feature is used.

Signed-off-by: Mike Snitzer <snitzer@kernel.org>

diff --git a/drivers/md/dm-verity-target.c b/drivers/md/dm-verity-target.c
index 4895d6b305595715ed164fd8afe52b5d0b9cea24..d287d01b7684343fb49e2d89cce57cb16ea9a06e 100644 (file)
--- a/drivers/md/dm-verity-target.c
+++ b/drivers/md/dm-verity-target.c
@@ -19,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/reboot.h>
 #include <linux/scatterlist.h>
+#include <linux/jump_label.h>
 
 #define DM_MSG_PREFIX                  "verity"
 
@@ -43,6 +44,8 @@ static unsigned dm_verity_prefetch_cluster = DM_VERITY_DEFAULT_PREFETCH_SIZE;
 
 module_param_named(prefetch_cluster, dm_verity_prefetch_cluster, uint, S_IRUGO | S_IWUSR);
 
+static DEFINE_STATIC_KEY_FALSE(use_tasklet_enabled);
+
 struct dm_verity_prefetch_work {
        struct work_struct work;
        struct dm_verity *v;
@@ -287,7 +290,7 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
 
        verity_hash_at_level(v, block, level, &hash_block, &offset);
 
-       if (io->in_tasklet) {
+       if (static_branch_unlikely(&use_tasklet_enabled) && io->in_tasklet) {
                data = dm_bufio_get(v->bufio, hash_block, &buf);
                if (data == NULL) {
                        /*
@@ -320,7 +323,8 @@ static int verity_verify_level(struct dm_verity *v, struct dm_verity_io *io,
                if (likely(memcmp(verity_io_real_digest(v, io), want_digest,
                                  v->digest_size) == 0))
                        aux->hash_verified = 1;
-               else if (io->in_tasklet) {
+               else if (static_branch_unlikely(&use_tasklet_enabled) &&
+                        io->in_tasklet) {
                        /*
                         * Error handling code (FEC included) cannot be run in a
                         * tasklet since it may sleep, so fallback to work-queue.
@@ -553,7 +557,8 @@ static int verity_verify_io(struct dm_verity_io *io)
                        if (v->validated_blocks)
                                set_bit(cur_block, v->validated_blocks);
                        continue;
-               } else if (io->in_tasklet) {
+               } else if (static_branch_unlikely(&use_tasklet_enabled) &&
+                          io->in_tasklet) {
                        /*
                         * Error handling code (FEC included) cannot be run in a
                         * tasklet since it may sleep, so fallback to work-queue.
@@ -598,7 +603,7 @@ static void verity_finish_io(struct dm_verity_io *io, blk_status_t status)
        bio->bi_end_io = io->orig_bi_end_io;
        bio->bi_status = status;
 
-       if (!io->in_tasklet)
+       if (!static_branch_unlikely(&use_tasklet_enabled) || !io->in_tasklet)
                verity_fec_finish_io(io);
 
        bio_endio(bio);
@@ -641,7 +646,7 @@ static void verity_end_io(struct bio *bio)
                return;
        }
 
-       if (io->v->use_tasklet) {
+       if (static_branch_unlikely(&use_tasklet_enabled) && io->v->use_tasklet) {
                tasklet_init(&io->tasklet, verity_tasklet, (unsigned long)io);
                tasklet_schedule(&io->tasklet);
        } else {
@@ -949,6 +954,9 @@ static void verity_dtr(struct dm_target *ti)
 
        kfree(v->signature_key_desc);
 
+       if (v->use_tasklet)
+               static_branch_dec(&use_tasklet_enabled);
+
        kfree(v);
 }
 
@@ -1080,6 +1088,7 @@ static int verity_parse_opt_args(struct dm_arg_set *as, struct dm_verity *v,
 
                } else if (!strcasecmp(arg_name, DM_VERITY_OPT_TASKLET_VERIFY)) {
                        v->use_tasklet = true;
+                       static_branch_inc(&use_tasklet_enabled);
                        continue;
 
                } else if (verity_is_fec_opt_arg(arg_name)) {