io_uring: remove FFS_SCM

THe lifetime of SCM'ed files is bound to ring_sock, which is destroyed
strictly after we're done with registered file tables. This means there
is no need for the FFS_SCM hack, which was not available on 32-bit builds
anyway.

Signed-off-by: Pavel Begunkov <[email protected]>
Link: https://lore.kernel.org/r/984226a1045adf42dc35d8bd7fb5a8bbfa472ce1.1665891182.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <[email protected]>

Author: isilence

io_uring/filetable.h

@@ -5,22 +5,9 @@
 #include <linux/file.h>
 #include <linux/io_uring_types.h>
 
-/*
- * FFS_SCM is only available on 64-bit archs, for 32-bit we just define it as 0
- * and define IO_URING_SCM_ALL. For this case, we use SCM for all files as we
- * can't safely always dereference the file when the task has exited and ring
- * cleanup is done. If a file is tracked and part of SCM, then unix gc on
- * process exit may reap it before __io_sqe_files_unregister() is run.
- */
 #define FFS_NOWAIT		0x1UL
 #define FFS_ISREG		0x2UL
-#if defined(CONFIG_64BIT)
-#define FFS_SCM			0x4UL
-#else
-#define IO_URING_SCM_ALL
-#define FFS_SCM			0x0UL
-#endif
-#define FFS_MASK		~(FFS_NOWAIT|FFS_ISREG|FFS_SCM)
+#define FFS_MASK		~(FFS_NOWAIT|FFS_ISREG)
 
 bool io_alloc_file_tables(struct io_file_table *table, unsigned nr_files);
 void io_free_file_tables(struct io_file_table *table);

io_uring/io_uring.c

@@ -1587,8 +1587,6 @@ unsigned int io_file_get_flags(struct file *file)
 		res |= FFS_ISREG;
 	if (__io_file_supports_nowait(file, mode))
 		res |= FFS_NOWAIT;
-	if (io_file_need_scm(file))
-		res |= FFS_SCM;
 	return res;
 }
 

io_uring/rsrc.c

@@ -757,20 +757,17 @@ int io_queue_rsrc_removal(struct io_rsrc_data *data, unsigned idx,
 
 void __io_sqe_files_unregister(struct io_ring_ctx *ctx)
 {
-#if !defined(IO_URING_SCM_ALL)
 	int i;
 
 	for (i = 0; i < ctx->nr_user_files; i++) {
 		struct file *file = io_file_from_index(&ctx->file_table, i);
 
-		if (!file)
-			continue;
-		if (io_fixed_file_slot(&ctx->file_table, i)->file_ptr & FFS_SCM)
+		/* skip scm accounted files, they'll be freed by ->ring_sock */
+		if (!file || io_file_need_scm(file))
 			continue;
 		io_file_bitmap_clear(&ctx->file_table, i);
 		fput(file);
 	}
-#endif
 
 #if defined(CONFIG_UNIX)
 	if (ctx->ring_sock) {

io_uring/rsrc.h

@@ -82,11 +82,7 @@ int __io_scm_file_account(struct io_ring_ctx *ctx, struct file *file);
 #if defined(CONFIG_UNIX)
 static inline bool io_file_need_scm(struct file *filp)
 {
-#if defined(IO_URING_SCM_ALL)
-	return true;
-#else
 	return !!unix_get_socket(filp);
-#endif
 }
 #else
 static inline bool io_file_need_scm(struct file *filp)