fs/aio: add configurable AIO_LISTIO_MAX limit

lio_listio() never validated 'nent' against {AIO_LISTIO_MAX}, so a
batch larger than the documented limit was silently accepted, and the
hard-coded _POSIX_AIO_LISTIO_MAX value of 2 was too small for real
workloads (LTP uses 10 entries per call).

Add the FS_AIO_LISTIO_MAX Kconfig option (default 10), use it for
_POSIX_AIO_LISTIO_MAX in include/limits.h, validate 'nent' in
lio_listio(), and report the limit through sysconf(_SC_AIO_LISTIO_MAX).

Signed-off-by: tengshuangshuang <tengshuangshuang@xiaomi.com>

fs/aio/Kconfig

@@ -11,6 +11,18 @@ config FS_AIO
 		Enable support for asynchronous I/O.  This selection enables the
 		interfaces declared in include/aio.h.
 
+config FS_AIO_LISTIO_MAX
+	int "Maximum number of AIO operations in listio"
+	default 10
+	---help---
+		This option sets the maximum number of asynchronous I/O (AIO) operations
+		that can be submitted in a single call to lio_listio().
+
+		This value defines the upper limit for the 'nent' parameter in
+		lio_listio(mode, aiocb_list, nent, sevp). Increasing this value allows
+		more operations to be queued.
+		Default: 10
+
 if FS_AIO
 
 config FS_NAIOC

fs/aio/lio_listio.c

@@ -334,7 +334,8 @@ int lio_listio(int mode, FAR struct aiocb *restrict const list[restrict],
   int ret;
   int i;
 
-  if (mode != LIO_WAIT && mode != LIO_NOWAIT)
+  if (nent < 0 || nent > AIO_LISTIO_MAX ||
+      (mode != LIO_WAIT && mode != LIO_NOWAIT))
     {
       set_errno(EINVAL);
       return ERROR;

include/limits.h

@@ -188,7 +188,7 @@
 
 /* Required for asynchronous I/O */
 
-#define _POSIX_AIO_LISTIO_MAX 2
+#define _POSIX_AIO_LISTIO_MAX CONFIG_FS_AIO_LISTIO_MAX
 #define _POSIX_AIO_MAX        1
 
 /* Required for POSIX message passing */

libs/libc/unistd/lib_sysconf.c

@@ -266,6 +266,9 @@ long sysconf(int name)
       case _SC_THREAD_THREADS_MAX:
         return UINT8_MAX;
 
+      case _SC_AIO_LISTIO_MAX:
+        return AIO_LISTIO_MAX;
+
       default:
 #if 0 /* Assume valid but not implemented for the time being */
         errcode = EINVAL;