[PATCH 1/3] io-wq: add support for inheriting ->fs

[Jens Axboe <axboe@kernel.dk>]

Some work items need this for relative path lookup, make it available
like the other inherited credentials/mm/etc.

Cc: stable@vger.kernel.org # 5.3+
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io-wq.c | 19 +++++++++++++++----
 fs/io-wq.h |  4 +++-
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index cb60a42b9fdf..58b1891bcfe5 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -16,6 +16,7 @@
 #include <linux/slab.h>
 #include <linux/kthread.h>
 #include <linux/rculist_nulls.h>
+#include <linux/fs_struct.h>
 
 #include "io-wq.h"
 
@@ -59,6 +60,7 @@ struct io_worker {
 	const struct cred *cur_creds;
 	const struct cred *saved_creds;
 	struct files_struct *restore_files;
+	struct fs_struct *restore_fs;
 };
 
 #if BITS_PER_LONG == 64
@@ -141,13 +143,17 @@ static bool __io_worker_unuse(struct io_wqe *wqe, struct io_worker *worker)
 		worker->cur_creds = worker->saved_creds = NULL;
 	}
 
-	if (current->files != worker->restore_files) {
+	if ((current->files != worker->restore_files) ||
+	    (current->fs != worker->restore_fs)) {
 		__acquire(&wqe->lock);
 		spin_unlock_irq(&wqe->lock);
 		dropped_lock = true;
 
 		task_lock(current);
-		current->files = worker->restore_files;
+		if (current->files != worker->restore_files)
+			current->files = worker->restore_files;
+		if (current->fs != worker->restore_fs)
+			current->fs = worker->restore_fs;
 		task_unlock(current);
 	}
 
@@ -311,6 +317,7 @@ static void io_worker_start(struct io_wqe *wqe, struct io_worker *worker)
 
 	worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING);
 	worker->restore_files = current->files;
+	worker->restore_fs = current->fs;
 	io_wqe_inc_running(wqe, worker);
 }
 
@@ -476,9 +483,13 @@ static void io_worker_handle_work(struct io_worker *worker)
 		if (work->flags & IO_WQ_WORK_CB)
 			work->func(&work);
 
-		if (work->files && current->files != work->files) {
+		if ((work->files && current->files != work->files) ||
+		    (work->fs && current->fs != work->fs)) {
 			task_lock(current);
-			current->files = work->files;
+			if (work->files && current->files != work->files)
+				current->files = work->files;
+			if (work->fs && current->fs != work->fs)
+				current->fs = work->fs;
 			task_unlock(current);
 		}
 		if (work->mm != worker->mm)
diff --git a/fs/io-wq.h b/fs/io-wq.h
index 50b3378febf2..f152ba677d8f 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -74,6 +74,7 @@ struct io_wq_work {
 	struct files_struct *files;
 	struct mm_struct *mm;
 	const struct cred *creds;
+	struct fs_struct *fs;
 	unsigned flags;
 };
 
@@ -81,10 +82,11 @@ struct io_wq_work {
 	do {						\
 		(work)->list.next = NULL;		\
 		(work)->func = _func;			\
-		(work)->flags = 0;			\
 		(work)->files = NULL;			\
 		(work)->mm = NULL;			\
 		(work)->creds = NULL;			\
+		(work)->fs = NULL;			\
+		(work)->flags = 0;			\
 	} while (0)					\
 
 typedef void (get_work_fn)(struct io_wq_work *);
-- 
2.25.0