[PATCH 13/23] nvmet: add context annotation for nvmet_ns::buffered_io

[Nilay Shroff <nilay@linux.ibm.com>]

The nvmet_ns::buffered_io field is protected by nvmet_subsys::lock.
Annotate it with __guarded_by(&subsys->lock) so that the clang context
analyzer can validate accesses to this field.

Some accesses to nvmet_ns::buffered_io in the I/O hotpath do not require
holding nvmet_subsys::lock, as the namespace reference guarantees that
the namespace remains valid and the field is not modified while I/O is
in flight. However, the clang context analyzer cannot express this
access pattern directly.

Introduce nvmet_ns_buffered_io() as an inline helper annotated with
__context_unsafe() to allow these accesses without requiring the
subsystem lock. Convert the relevant accesses in the I/O hotpath and
request-processing paths to use this helper.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 drivers/nvme/target/io-cmd-file.c | 2 +-
 drivers/nvme/target/nvmet.h       | 4 +++-
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/target/io-cmd-file.c b/drivers/nvme/target/io-cmd-file.c
index 224b7423b780..295203f10c2e 100644
--- a/drivers/nvme/target/io-cmd-file.c
+++ b/drivers/nvme/target/io-cmd-file.c
@@ -239,7 +239,7 @@ static void nvmet_file_execute_rw(struct nvmet_req *req)
 	} else
 		req->f.mpool_alloc = false;
 
-	if (req->ns->buffered_io) {
+	if (nvmet_ns_buffered_io(req->ns)) {
 		if (likely(!req->f.mpool_alloc) &&
 		    (nvmet_ns_file(req->ns)->f_mode & FMODE_NOWAIT) &&
 		    nvmet_file_execute_io(req, IOCB_NOWAIT))
diff --git a/drivers/nvme/target/nvmet.h b/drivers/nvme/target/nvmet.h
index 3e18c36e83c8..572f495b06df 100644
--- a/drivers/nvme/target/nvmet.h
+++ b/drivers/nvme/target/nvmet.h
@@ -169,7 +169,8 @@ struct nvmet_ns {
 		__guarded_by(&subsys->lock);
 	u32			anagrpid;
 
-	bool			buffered_io;
+	bool			buffered_io
+		__guarded_by(&subsys->lock);
 	bool			enabled;
 #define NVMET_NS_IO_LIVE	0
 	unsigned long		flags;
@@ -214,6 +215,7 @@ NVMET_NS_ACCESSOR(u32, nsid)
 NVMET_NS_ACCESSOR(u32, blksize_shift)
 NVMET_NS_ACCESSOR(u8 *, nguid)
 NVMET_NS_ACCESSOR(uuid_t, uuid)
+NVMET_NS_ACCESSOR(bool, buffered_io)
 
 /*
  * These accessors use data_race() and READ_ONCE() to allow lockless access to
-- 
2.53.0