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do_sys_poll: simplify playing with on-stack data

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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 <oleg@tv-sign.ru>
Looks-good-to: Andi Kleen <ak@suse.de>
Cc: Davide Libenzi <davidel@xmailserver.org>
Cc: Vadim Lobanov <vlobanov@speakeasy.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-10-16 23:26:17 -07:00 committed by Linus Torvalds
parent 759d7c6c47
commit 252e5725cf
1 changed files with 36 additions and 56 deletions
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92
fs/select.c
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@ -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;
walk = pp;
if (copy_from_user(pp->entries, ufds + nfds-i,
sizeof(struct pollfd)*num)) {
err = -EFAULT;
todo -= walk->len;
if (!todo)
break;
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;
}