[PATCH 1/4] io_uring: grab owning task fs_struct

[Jens Axboe <axboe@kernel.dk>]

We need this for work that operates on relative paths.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/io_uring.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ba97bb433922..da6a5998fa30 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -75,6 +75,7 @@
 #include <linux/fsnotify.h>
 #include <linux/fadvise.h>
 #include <linux/eventpoll.h>
+#include <linux/fs_struct.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/io_uring.h>
@@ -264,6 +265,8 @@ struct io_ring_ctx {
 
 	const struct cred	*creds;
 
+	struct fs_struct	*fs;
+
 	/* 0 is for ctx quiesce/reinit/free, 1 is for sqo_thread started */
 	struct completion	*completions;
 
@@ -6261,6 +6264,16 @@ static void io_ring_ctx_free(struct io_ring_ctx *ctx)
 	if (ctx->account_mem)
 		io_unaccount_mem(ctx->user,
 				ring_pages(ctx->sq_entries, ctx->cq_entries));
+	if (ctx->fs) {
+		struct fs_struct *fs = ctx->fs;
+
+		spin_lock(&ctx->fs->lock);
+		if (--fs->users)
+			fs = NULL;
+		spin_unlock(&ctx->fs->lock);
+		if (fs)
+			free_fs_struct(fs);
+	}
 	free_uid(ctx->user);
 	put_cred(ctx->creds);
 	kfree(ctx->completions);
@@ -6768,6 +6781,13 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
 	ctx->user = user;
 	ctx->creds = get_current_cred();
 
+	task_lock(current);
+	spin_lock(&current->fs->lock);
+	ctx->fs = current->fs;
+	ctx->fs->users++;
+	spin_unlock(&current->fs->lock);
+	task_unlock(current);
+
 	ret = io_allocate_scq_urings(ctx, p);
 	if (ret)
 		goto err;
-- 
2.25.0