[PATCH 5.4 001/152] io_uring: grab ->fs as part of async offload

Greg Kroah-Hartman
2020-03-03T18:09:31Z

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commits 9392a27d88b9 and ff002b30181d ]

Ensure that the async work grabs ->fs from the queueing task if the
punted commands needs to do lookups.

We don't have these two commits in 5.4-stable:

ff002b30181d30cdfbca316dadd099c3ca0d739c
9392a27d88b9707145d713654eb26f0c29789e50

because they don't apply with the rework that was done in how io_uring
handles offload. Since there's no io-wq in 5.4, it doesn't make sense to
do two patches. I'm attaching my port of the two for 5.4-stable, it's
been tested. Please queue it up for the next 5.4-stable, thanks!

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index ed9a551882cf3..f34a8f7eee5d1 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -71,6 +71,7 @@
#include <linux/sizes.h>
#include <linux/hugetlb.h>
#include <linux/highmem.h>
+#include <linux/fs_struct.h>

#include <uapi/linux/io_uring.h>

@@ -334,6 +335,8 @@ struct io_kiocb {
u32 result;
u32 sequence;

+ struct fs_struct *fs;
+
struct work_struct work;
};

@@ -651,6 +654,7 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
/* one is dropped after submission, the other at completion */
refcount_set(&req->refs, 2);
req->result = 0;
+ req->fs = NULL;
return req;
out:
percpu_ref_put(&ctx->refs);
@@ -1663,6 +1667,16 @@ static int io_send_recvmsg(struct io_kiocb *req, const struct io_uring_sqe *sqe,
ret = -EINTR;
}

+ if (req->fs) {
+ struct fs_struct *fs = req->fs;
+
+ spin_lock(&req->fs->lock);
+ if (--fs->users)
+ fs = NULL;
+ spin_unlock(&req->fs->lock);
+ if (fs)
+ free_fs_struct(fs);
+ }
io_cqring_add_event(req->ctx, sqe->user_data, ret);
io_put_req(req);
return 0;
@@ -2159,6 +2173,7 @@ static inline bool io_sqe_needs_user(const struct io_uring_sqe *sqe)
static void io_sq_wq_submit_work(struct work_struct *work)
{
struct io_kiocb *req = container_of(work, struct io_kiocb, work);
+ struct fs_struct *old_fs_struct = current->fs;
struct io_ring_ctx *ctx = req->ctx;
struct mm_struct *cur_mm = NULL;
struct async_list *async_list;
@@ -2178,6 +2193,15 @@ restart:
/* Ensure we clear previously set non-block flag */
req->rw.ki_flags &= ~IOCB_NOWAIT;

+ if (req->fs != current->fs && current->fs != old_fs_struct) {
+ task_lock(current);
+ if (req->fs)
+ current->fs = req->fs;
+ else
+ current->fs = old_fs_struct;
+ task_unlock(current);
+ }
+
ret = 0;
if (io_sqe_needs_user(sqe) && !cur_mm) {
if (!mmget_not_zero(ctx->sqo_mm)) {
@@ -2276,6 +2300,11 @@ out:
mmput(cur_mm);
}
revert_creds(old_cred);
+ if (old_fs_struct) {
+ task_lock(current);
+ current->fs = old_fs_struct;
+ task_unlock(current);
+ }
}

/*
@@ -2503,6 +2532,23 @@ err:

req->user_data = s->sqe->user_data;

+#if defined(CONFIG_NET)
+ switch (READ_ONCE(s->sqe->opcode)) {
+ case IORING_OP_SENDMSG:
+ case IORING_OP_RECVMSG:
+ spin_lock(&current->fs->lock);
+ if (!current->fs->in_exec) {
+ req->fs = current->fs;
+ req->fs->users++;
+ }
+ spin_unlock(&current->fs->lock);
+ if (!req->fs) {
+ ret = -EAGAIN;
+ goto err_req;
+ }
+ }
+#endif
+
/*
* If we already have a head request, queue this one for async
* submittal once the head completes. If we don't have a head but
--
2.20.1