io_uring: grab ->fs as part of async preparation

This passes it in to io-wq, so it assumes the right fs_struct when
executing async work that may need to do lookups.

Cc: stable@vger.kernel.org # 5.3+
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1a3ca65..2a7bb17 100644 (file)
--- 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>
@@ -611,6 +612,8 @@ struct io_op_def {
        unsigned                not_supported : 1;
        /* needs file table */
        unsigned                file_table : 1;
+       /* needs ->fs */
+       unsigned                needs_fs : 1;
 };
 
 static const struct io_op_def io_op_defs[] = {
@@ -653,12 +656,14 @@ static const struct io_op_def io_op_defs[] = {
                .needs_mm               = 1,
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
+               .needs_fs               = 1,
        },
        [IORING_OP_RECVMSG] = {
                .async_ctx              = 1,
                .needs_mm               = 1,
                .needs_file             = 1,
                .unbound_nonreg_file    = 1,
+               .needs_fs               = 1,
        },
        [IORING_OP_TIMEOUT] = {
                .async_ctx              = 1,
@@ -689,6 +694,7 @@ static const struct io_op_def io_op_defs[] = {
                .needs_file             = 1,
                .fd_non_neg             = 1,
                .file_table             = 1,
+               .needs_fs               = 1,
        },
        [IORING_OP_CLOSE] = {
                .needs_file             = 1,
@@ -702,6 +708,7 @@ static const struct io_op_def io_op_defs[] = {
                .needs_mm               = 1,
                .needs_file             = 1,
                .fd_non_neg             = 1,
+               .needs_fs               = 1,
        },
        [IORING_OP_READ] = {
                .needs_mm               = 1,
@@ -733,6 +740,7 @@ static const struct io_op_def io_op_defs[] = {
                .needs_file             = 1,
                .fd_non_neg             = 1,
                .file_table             = 1,
+               .needs_fs               = 1,
        },
        [IORING_OP_EPOLL_CTL] = {
                .unbound_nonreg_file    = 1,
@@ -907,6 +915,16 @@ static inline void io_req_work_grab_env(struct io_kiocb *req,
        }
        if (!req->work.creds)
                req->work.creds = get_current_cred();
+       if (!req->work.fs && def->needs_fs) {
+               spin_lock(&current->fs->lock);
+               if (!current->fs->in_exec) {
+                       req->work.fs = current->fs;
+                       req->work.fs->users++;
+               } else {
+                       req->work.flags |= IO_WQ_WORK_CANCEL;
+               }
+               spin_unlock(&current->fs->lock);
+       }
 }
 
 static inline void io_req_work_drop_env(struct io_kiocb *req)
@@ -919,6 +937,16 @@ static inline void io_req_work_drop_env(struct io_kiocb *req)
                put_cred(req->work.creds);
                req->work.creds = NULL;
        }
+       if (req->work.fs) {
+               struct fs_struct *fs = req->work.fs;
+
+               spin_lock(&req->work.fs->lock);
+               if (--fs->users)
+                       fs = NULL;
+               spin_unlock(&req->work.fs->lock);
+               if (fs)
+                       free_fs_struct(fs);
+       }
 }
 
 static inline bool io_prep_async_work(struct io_kiocb *req,