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-rw-r--r--include/linux/file.h28
1 files changed, 24 insertions, 4 deletions
diff --git a/include/linux/file.h b/include/linux/file.h
index 9901b850f2e4..9f7c2513866f 100644
--- a/include/linux/file.h
+++ b/include/linux/file.h
@@ -10,6 +10,7 @@
#include <linux/compiler.h>
#include <linux/spinlock.h>
#include <linux/rcupdate.h>
+#include <linux/types.h>
/*
* The default fd array needs to be at least BITS_PER_LONG,
@@ -17,10 +18,22 @@
*/
#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];
+};
+
+/*
+ * More than this number of fds: we use a separately allocated fd_set
+ */
+#define EMBEDDED_FD_SET_SIZE (BITS_PER_BYTE * sizeof(struct embedded_fd_set))
+
struct fdtable {
unsigned int max_fds;
int max_fdset;
- int next_fd;
struct file ** fd; /* current fd array */
fd_set *close_on_exec;
fd_set *open_fds;
@@ -33,13 +46,20 @@ struct fdtable {
* Open file table structure
*/
struct files_struct {
+ /*
+ * read mostly part
+ */
atomic_t count;
struct fdtable *fdt;
struct fdtable fdtab;
- fd_set close_on_exec_init;
- fd_set open_fds_init;
+ /*
+ * written part on a separate cache line in SMP
+ */
+ 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;
struct file * fd_array[NR_OPEN_DEFAULT];
- spinlock_t file_lock; /* Protects concurrent writers. Nests inside tsk->alloc_lock */
};
#define files_fdtable(files) (rcu_dereference((files)->fdt))