Wrap accesses to the fd_sets in struct fdtable
Wrap accesses to the fd_sets in struct fdtable (for recording open files and
close-on-exec flags) so that we can move away from using fd_sets since we
abuse the fd_set structs by not allocating the full-sized structure under
normal circumstances and by non-core code looking at the internals of the
fd_sets.
The first abuse means that use of FD_ZERO() on these fd_sets is not permitted,
since that cannot be told about their abnormal lengths.
This introduces six wrapper functions for setting, clearing and testing
close-on-exec flags and fd-is-open flags:
void __set_close_on_exec(int fd, struct fdtable *fdt);
void __clear_close_on_exec(int fd, struct fdtable *fdt);
bool close_on_exec(int fd, const struct fdtable *fdt);
void __set_open_fd(int fd, struct fdtable *fdt);
void __clear_open_fd(int fd, struct fdtable *fdt);
bool fd_is_open(int fd, const struct fdtable *fdt);
Note that I've prepended '__' to the names of the set/clear functions because
they require the caller to hold a lock to use them.
Note also that I haven't added wrappers for looking behind the scenes at the
the array. Possibly that should exist too.
Signed-off-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/20120216174942.23314.1364.stgit@warthog.procyon.org.uk
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 22764c7..75e7c1f 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -32,20 +32,20 @@
spin_lock(&files->file_lock);
fdt = files_fdtable(files);
if (flag)
- FD_SET(fd, fdt->close_on_exec);
+ __set_close_on_exec(fd, fdt);
else
- FD_CLR(fd, fdt->close_on_exec);
+ __clear_close_on_exec(fd, fdt);
spin_unlock(&files->file_lock);
}
-static int get_close_on_exec(unsigned int fd)
+static bool get_close_on_exec(unsigned int fd)
{
struct files_struct *files = current->files;
struct fdtable *fdt;
- int res;
+ bool res;
rcu_read_lock();
fdt = files_fdtable(files);
- res = FD_ISSET(fd, fdt->close_on_exec);
+ res = close_on_exec(fd, fdt);
rcu_read_unlock();
return res;
}
@@ -90,15 +90,15 @@
err = -EBUSY;
fdt = files_fdtable(files);
tofree = fdt->fd[newfd];
- if (!tofree && FD_ISSET(newfd, fdt->open_fds))
+ if (!tofree && fd_is_open(newfd, fdt))
goto out_unlock;
get_file(file);
rcu_assign_pointer(fdt->fd[newfd], file);
- FD_SET(newfd, fdt->open_fds);
+ __set_open_fd(newfd, fdt);
if (flags & O_CLOEXEC)
- FD_SET(newfd, fdt->close_on_exec);
+ __set_close_on_exec(newfd, fdt);
else
- FD_CLR(newfd, fdt->close_on_exec);
+ __clear_close_on_exec(newfd, fdt);
spin_unlock(&files->file_lock);
if (tofree)