new helper: __alloc_fd()

Essentially, alloc_fd() in a files_struct we own a reference to.
Most of the time wanting to use it is a sign of lousy API
design (such as android/binder).  It's *not* a general-purpose
interface; better that than open-coding its guts, but again,
playing with other process' descriptor table is a sign of bad
design.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/file.c b/fs/file.c
index 08922af4a62c..a3a0705f8f51 100644
--- a/fs/file.c
+++ b/fs/file.c
@@ -420,11 +420,10 @@ struct files_struct init_files = {
 /*
  * allocate a file descriptor, mark it busy.
  */
-int alloc_fd(unsigned start, unsigned flags)
+int __alloc_fd(struct files_struct *files,
+               unsigned start, unsigned end, unsigned flags)
 {
-        struct files_struct *files = current->files;
         unsigned int fd;
-        unsigned end = rlimit(RLIMIT_NOFILE);
         int error;
         struct fdtable *fdt;
 
@@ -479,8 +478,13 @@ out:
         return error;
 }
 
+int alloc_fd(unsigned start, unsigned flags)
+{
+        return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
+}
+
 int get_unused_fd_flags(unsigned flags)
 {
-        return alloc_fd(0, flags);
+        return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags);
 }
 EXPORT_SYMBOL(get_unused_fd_flags);