The patch titled
do_sys_poll: simplify playing with on-stack data
has been added to the -mm tree. Its filename is
do_sys_poll-simplify-playing-with-on-stack-data.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: do_sys_poll: simplify playing with on-stack data
From: Oleg Nesterov <oleg@xxxxxxxxxx>
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.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Looks-good-to: Andi Kleen <ak@xxxxxxx>
Cc: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
Cc: Vadim Lobanov <vlobanov@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/select.c | 92 +++++++++++++++++++-------------------------------
1 files changed, 36 insertions(+), 56 deletions(-)
diff -puN fs/select.c~do_sys_poll-simplify-playing-with-on-stack-data fs/select.c
--- a/fs/select.c~do_sys_poll-simplify-playing-with-on-stack-data
+++ a/fs/select.c
@@ -653,86 +653,66 @@ static int do_poll(unsigned int nfds, s
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(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;
}
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
origin.patch
clone-flag-clone_parent_tidptr-leaves-invalid-results-in-memory.patch
sys_time-use-barrier-instead-of-smp_rmb.patch
do_sys_poll-simplify-playing-with-on-stack-data.patch
do_poll-return-eintr-when-signalled.patch
-
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