From 252e5725cfb55a89e54888317856903fef9d5031 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Tue, 16 Oct 2007 23:26:17 -0700 Subject: [PATCH] do_sys_poll: simplify playing with on-stack data Cleanup. Lessens both the source and compiled code (100 bytes) and imho makes the code much more understandable. With this patch "struct poll_list *head" always points to on-stack stack_pps, so we can remove all "is it on-stack" and "was it initialized" checks. Also, move poll_initwait/poll_freewait and -EINTR detection closer to the do_poll()'s callsite. [akpm@linux-foundation.org: fix warning (size_t != uint)] Signed-off-by: Oleg Nesterov Looks-good-to: Andi Kleen Cc: Davide Libenzi Cc: Vadim Lobanov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/select.c | 92 +++++++++++++++++++++-------------------------------- 1 file changed, 36 insertions(+), 56 deletions(-) diff --git a/fs/select.c b/fs/select.c index 46dca31c60..41c3571e64 100644 --- a/fs/select.c +++ b/fs/select.c @@ -651,86 +651,66 @@ static int do_poll(unsigned int nfds, struct poll_list *list, int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout) { struct poll_wqueues table; - int fdcount, err; - unsigned int i; - struct poll_list *head; - struct poll_list *walk; + int err = -EFAULT, fdcount, len, size; /* Allocate small arguments on the stack to save memory and be faster - use long to make sure the buffer is aligned properly on 64 bit archs to avoid unaligned access */ long stack_pps[POLL_STACK_ALLOC/sizeof(long)]; - struct poll_list *stack_pp = NULL; + struct poll_list *const head = (struct poll_list *)stack_pps; + struct poll_list *walk = head; + unsigned long todo = nfds; - /* Do a sanity check on nfds ... */ if (nfds > current->signal->rlim[RLIMIT_NOFILE].rlim_cur) return -EINVAL; - poll_initwait(&table); + len = min_t(unsigned int, nfds, N_STACK_PPS); + for (;;) { + walk->next = NULL; + walk->len = len; + if (!len) + break; - head = NULL; - walk = NULL; - i = nfds; - err = -ENOMEM; - while(i!=0) { - struct poll_list *pp; - int num, size; - if (stack_pp == NULL) - num = N_STACK_PPS; - else - num = POLLFD_PER_PAGE; - if (num > i) - num = i; - size = sizeof(struct poll_list) + sizeof(struct pollfd)*num; - if (!stack_pp) - stack_pp = pp = (struct poll_list *)stack_pps; - else { - pp = kmalloc(size, GFP_KERNEL); - if (!pp) - goto out_fds; - } - pp->next=NULL; - pp->len = num; - if (head == NULL) - head = pp; - else - walk->next = pp; + if (copy_from_user(walk->entries, ufds + nfds-todo, + sizeof(struct pollfd) * walk->len)) + goto out_fds; + + todo -= walk->len; + if (!todo) + break; - walk = pp; - if (copy_from_user(pp->entries, ufds + nfds-i, - sizeof(struct pollfd)*num)) { - err = -EFAULT; + len = min(todo, POLLFD_PER_PAGE); + size = sizeof(struct poll_list) + sizeof(struct pollfd) * len; + walk = walk->next = kmalloc(size, GFP_KERNEL); + if (!walk) { + err = -ENOMEM; goto out_fds; } - i -= pp->len; } + poll_initwait(&table); fdcount = do_poll(nfds, head, &table, timeout); + if (!fdcount && signal_pending(current)) + fdcount = -EINTR; + poll_freewait(&table); - /* OK, now copy the revents fields back to user space. */ - walk = head; - err = -EFAULT; - while(walk != NULL) { + for (walk = head; walk; walk = walk->next) { struct pollfd *fds = walk->entries; int j; - for (j=0; j < walk->len; j++, ufds++) { - if(__put_user(fds[j].revents, &ufds->revents)) + for (j = 0; j < walk->len; j++, ufds++) + if (__put_user(fds[j].revents, &ufds->revents)) goto out_fds; - } - walk = walk->next; } + err = fdcount; - if (!fdcount && signal_pending(current)) - err = -EINTR; out_fds: - walk = head; - while(walk!=NULL) { - struct poll_list *pp = walk->next; - if (walk != stack_pp) - kfree(walk); - walk = pp; + walk = head->next; + while (walk) { + struct poll_list *pos = walk; + walk = walk->next; + kfree(pos); } - poll_freewait(&table); + return err; } -- 2.39.5