Replace the fd_sets in struct fdtable with an array of unsigned longs
Replace the fd_sets in struct fdtable with an array of unsigned longs and then
use the standard non-atomic bit operations rather than the FD_* macros.
This:
(1) Removes the abuses of struct fd_set:
(a) Since we don't want to allocate a full fd_set the vast majority of the
time, we actually, in effect, just allocate a just-big-enough array of
unsigned longs and cast it to an fd_set type - so why bother with the
fd_set at all?
(b) Some places outside of the core fdtable handling code (such as
SELinux) want to look inside the array of unsigned longs hidden inside
the fd_set struct for more efficient iteration over the entire set.
(2) Eliminates the use of FD_*() macros in the kernel completely.
(3) Permits the __FD_*() macros to be deleted entirely where not exposed to
userspace.
Signed-off-by: David Howells <dhowells@redhat.com>
Link: http://lkml.kernel.org/r/20120216174954.23314.48147.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/include/linux/fdtable.h b/include/linux/fdtable.h
index 7675da2..158a41e 100644
--- a/include/linux/fdtable.h
+++ b/include/linux/fdtable.h
@@ -21,51 +21,43 @@
*/
#define NR_OPEN_DEFAULT BITS_PER_LONG
-/*
- * The embedded_fd_set is a small fd_set,
- * suitable for most tasks (which open <= BITS_PER_LONG files)
- */
-struct embedded_fd_set {
- unsigned long fds_bits[1];
-};
-
struct fdtable {
unsigned int max_fds;
struct file __rcu **fd; /* current fd array */
- fd_set *close_on_exec;
- fd_set *open_fds;
+ unsigned long *close_on_exec;
+ unsigned long *open_fds;
struct rcu_head rcu;
struct fdtable *next;
};
static inline void __set_close_on_exec(int fd, struct fdtable *fdt)
{
- FD_SET(fd, fdt->close_on_exec);
+ __set_bit(fd, fdt->close_on_exec);
}
static inline void __clear_close_on_exec(int fd, struct fdtable *fdt)
{
- FD_CLR(fd, fdt->close_on_exec);
+ __clear_bit(fd, fdt->close_on_exec);
}
static inline bool close_on_exec(int fd, const struct fdtable *fdt)
{
- return FD_ISSET(fd, fdt->close_on_exec);
+ return test_bit(fd, fdt->close_on_exec);
}
static inline void __set_open_fd(int fd, struct fdtable *fdt)
{
- FD_SET(fd, fdt->open_fds);
+ __set_bit(fd, fdt->open_fds);
}
static inline void __clear_open_fd(int fd, struct fdtable *fdt)
{
- FD_CLR(fd, fdt->open_fds);
+ __clear_bit(fd, fdt->open_fds);
}
static inline bool fd_is_open(int fd, const struct fdtable *fdt)
{
- return FD_ISSET(fd, fdt->open_fds);
+ return test_bit(fd, fdt->open_fds);
}
/*
@@ -83,8 +75,8 @@
*/
spinlock_t file_lock ____cacheline_aligned_in_smp;
int next_fd;
- struct embedded_fd_set close_on_exec_init;
- struct embedded_fd_set open_fds_init;
+ unsigned long close_on_exec_init[1];
+ unsigned long open_fds_init[1];
struct file __rcu * fd_array[NR_OPEN_DEFAULT];
};