From 4804e382c117ce213cd5c43512cf4b1d71bb2650 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Mon, 11 Nov 2019 23:03:25 +0100 Subject: x86/ioperm: Share I/O bitmap if identical The I/O bitmap is duplicated on fork. That's wasting memory and slows down fork. There is no point to do so. As long as the bitmap is not modified it can be shared between threads and processes. Add a refcount and just share it on fork. If a task modifies the bitmap then it has to do the duplication if and only if it is shared. Signed-off-by: Thomas Gleixner Acked-by: Andy Lutomirski --- arch/x86/kernel/process.c | 39 ++++++--------------------------------- 1 file changed, 6 insertions(+), 33 deletions(-) (limited to 'arch/x86/kernel/process.c') diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 7ba4d54aec17..0b19c137c442 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -122,37 +122,13 @@ static int set_new_tls(struct task_struct *p, unsigned long tls) return do_set_thread_area_64(p, ARCH_SET_FS, tls); } -static inline int copy_io_bitmap(struct task_struct *tsk) -{ - struct io_bitmap *iobm = current->thread.io_bitmap; - - if (likely(!test_tsk_thread_flag(current, TIF_IO_BITMAP))) - return 0; - - tsk->thread.io_bitmap = kmemdup(iobm, sizeof(*iobm), GFP_KERNEL); - - if (!tsk->thread.io_bitmap) - return -ENOMEM; - - set_tsk_thread_flag(tsk, TIF_IO_BITMAP); - return 0; -} - -static inline void free_io_bitmap(struct task_struct *tsk) -{ - if (tsk->thread.io_bitmap) { - kfree(tsk->thread.io_bitmap); - tsk->thread.io_bitmap = NULL; - } -} - int copy_thread_tls(unsigned long clone_flags, unsigned long sp, unsigned long arg, struct task_struct *p, unsigned long tls) { struct inactive_task_frame *frame; struct fork_frame *fork_frame; struct pt_regs *childregs; - int ret; + int ret = 0; childregs = task_pt_regs(p); fork_frame = container_of(childregs, struct fork_frame, regs); @@ -199,16 +175,13 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long sp, task_user_gs(p) = get_user_gs(current_pt_regs()); #endif - ret = copy_io_bitmap(p); - if (ret) - return ret; - /* Set a new TLS for the child thread? */ - if (clone_flags & CLONE_SETTLS) { + if (clone_flags & CLONE_SETTLS) ret = set_new_tls(p, tls); - if (ret) - free_io_bitmap(p); - } + + if (!ret && unlikely(test_tsk_thread_flag(current, TIF_IO_BITMAP))) + io_bitmap_share(p); + return ret; } -- cgit v1.2.3