2 files changed, 81 insertions, 42 deletions

diff --git a/fs/select.c b/fs/select.c
index 1815a57d2255..d8b4f0722b8d 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -29,12 +29,6 @@
 #define ROUND_UP(x,y) (((x)+(y)-1)/(y))
 #define DEFAULT_POLLMASK (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
 
-struct poll_table_entry {
-        struct file * filp;
-        wait_queue_t wait;
-        wait_queue_head_t * wait_address;
-};
-
 struct poll_table_page {
         struct poll_table_page * next;
         struct poll_table_entry * entry;
@@ -64,13 +58,23 @@ void poll_initwait(struct poll_wqueues *pwq)
         init_poll_funcptr(&pwq->pt, __pollwait);
         pwq->error = 0;
         pwq->table = NULL;
+        pwq->inline_index = 0;
 }
 
 EXPORT_SYMBOL(poll_initwait);
 
+static void free_poll_entry(struct poll_table_entry *entry)
+{
+        remove_wait_queue(entry->wait_address,&entry->wait);
+        fput(entry->filp);
+}
+
 void poll_freewait(struct poll_wqueues *pwq)
 {
         struct poll_table_page * p = pwq->table;
+        int i;
+        for (i = 0; i < pwq->inline_index; i++)
+                free_poll_entry(pwq->inline_entries + i);
         while (p) {
                 struct poll_table_entry * entry;
                 struct poll_table_page *old;
@@ -78,8 +82,7 @@ void poll_freewait(struct poll_wqueues *pwq)
                 entry = p->entry;
                 do {
                         entry--;
-                        remove_wait_queue(entry->wait_address,&entry->wait);
-                        fput(entry->filp);
+                        free_poll_entry(entry);
                 } while (entry > p->entries);
                 old = p;
                 p = p->next;
@@ -89,12 +92,14 @@ void poll_freewait(struct poll_wqueues *pwq)
 
 EXPORT_SYMBOL(poll_freewait);
 
-static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
-                       poll_table *_p)
+static struct poll_table_entry *poll_get_entry(poll_table *_p)
 {
         struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt);
         struct poll_table_page *table = p->table;
 
+        if (p->inline_index < N_INLINE_POLL_ENTRIES)
+                return p->inline_entries + p->inline_index++;
+
         if (!table || POLL_TABLE_FULL(table)) {
                 struct poll_table_page *new_table;
 
@@ -102,7 +107,7 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
                 if (!new_table) {
                         p->error = -ENOMEM;
                         __set_current_state(TASK_RUNNING);
-                        return;
+                        return NULL;
                 }
                 new_table->entry = new_table->entries;
                 new_table->next = table;
@@ -110,16 +115,21 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
                 table = new_table;
         }
 
-        /* Add a new entry */
-        {
-                struct poll_table_entry * entry = table->entry;
-                table->entry = entry+1;
-                get_file(filp);
-                entry->filp = filp;
-                entry->wait_address = wait_address;
-                init_waitqueue_entry(&entry->wait, current);
-                add_wait_queue(wait_address,&entry->wait);
-        }
+        return table->entry++;
+}
+
+/* Add a new entry */
+static void __pollwait(struct file *filp, wait_queue_head_t *wait_address,
+                                poll_table *p)
+{
+        struct poll_table_entry *entry = poll_get_entry(p);
+        if (!entry)
+                return;
+        get_file(filp);
+        entry->filp = filp;
+        entry->wait_address = wait_address;
+        init_waitqueue_entry(&entry->wait, current);
+        add_wait_queue(wait_address,&entry->wait);
 }
 
 #define FDS_IN(fds, n)          (fds->in + n)
@@ -284,16 +294,6 @@ int do_select(int n, fd_set_bits *fds, s64 *timeout)
         return retval;
 }
 
-static void *select_bits_alloc(int size)
-{
-        return kmalloc(6 * size, GFP_KERNEL);
-}
-
-static void select_bits_free(void *bits, int size)
-{
-        kfree(bits);
-}
-
 /*
  * We can actually return ERESTARTSYS instead of EINTR, but I'd
  * like to be certain this leads to no problems. So I return
@@ -312,6 +312,8 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
         char *bits;
         int ret, size, max_fdset;
         struct fdtable *fdt;
+        /* Allocate small arguments on the stack to save memory and be faster */
+        char stack_fds[SELECT_STACK_ALLOC];
 
         ret = -EINVAL;
         if (n < 0)
@@ -332,7 +334,10 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
          */
         ret = -ENOMEM;
         size = FDS_BYTES(n);
-        bits = select_bits_alloc(size);
+        if (6*size < SELECT_STACK_ALLOC)
+                bits = stack_fds;
+        else
+                bits = kmalloc(6 * size, GFP_KERNEL);
         if (!bits)
                 goto out_nofds;
         fds.in      = (unsigned long *)  bits;
@@ -367,7 +372,8 @@ static int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                 ret = -EFAULT;
 
 out:
-        select_bits_free(bits, size);
+        if (bits != stack_fds)
+                kfree(bits);
 out_nofds:
         return ret;
 }
@@ -619,6 +625,9 @@ static int do_poll(unsigned int nfds,  struct poll_list *list,
         return count;
 }
 
+#define N_STACK_PPS ((sizeof(stack_pps) - sizeof(struct poll_list))  / \
+                        sizeof(struct pollfd))
+
 int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
 {
         struct poll_wqueues table;
@@ -628,6 +637,9 @@ int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
         struct poll_list *walk;
         struct fdtable *fdt;
         int max_fdset;
+        /* Allocate small arguments on the stack to save memory and be faster */
+        char stack_pps[POLL_STACK_ALLOC];
+        struct poll_list *stack_pp = NULL;
 
         /* Do a sanity check on nfds ... */
         rcu_read_lock();
@@ -645,14 +657,23 @@ int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
         err = -ENOMEM;
         while(i!=0) {
                 struct poll_list *pp;
-                pp = kmalloc(sizeof(struct poll_list)+
-                                sizeof(struct pollfd)*
-                                (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i),
-                                        GFP_KERNEL);
-                if(pp==NULL)
-                        goto out_fds;
+                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 = (i>POLLFD_PER_PAGE?POLLFD_PER_PAGE:i);
+                pp->len = num;
                 if (head == NULL)
                         head = pp;
                 else
@@ -660,7 +681,7 @@ int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, s64 *timeout)
 
                 walk = pp;
                 if (copy_from_user(pp->entries, ufds + nfds-i, 
-                                sizeof(struct pollfd)*pp->len)) {
+                                sizeof(struct pollfd)*num)) {
                         err = -EFAULT;
                         goto out_fds;
                 }
@@ -689,7 +710,8 @@ out_fds:
         walk = head;
         while(walk!=NULL) {
                 struct poll_list *pp = walk->next;
-                kfree(walk);
+                if (walk != stack_pp)
+                        kfree(walk);
                 walk = pp;
         }
         poll_freewait(&table);
diff --git a/include/linux/poll.h b/include/linux/poll.h
index 8e8f6098508a..51e1b56741fb 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -11,6 +11,15 @@
 #include <linux/mm.h>
 #include <asm/uaccess.h>
 
+/* ~832 bytes of stack space used max in sys_select/sys_poll before allocating
+   additional memory. */
+#define MAX_STACK_ALLOC 832
+#define FRONTEND_STACK_ALLOC    256
+#define SELECT_STACK_ALLOC      FRONTEND_STACK_ALLOC
+#define POLL_STACK_ALLOC        FRONTEND_STACK_ALLOC
+#define WQUEUES_STACK_ALLOC     (MAX_STACK_ALLOC - FRONTEND_STACK_ALLOC)
+#define N_INLINE_POLL_ENTRIES   (WQUEUES_STACK_ALLOC / sizeof(struct poll_table_entry))
+
 struct poll_table_struct;
 
 /* 
@@ -33,6 +42,12 @@ static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
         pt->qproc = qproc;
 }
 
+struct poll_table_entry {
+        struct file * filp;
+        wait_queue_t wait;
+        wait_queue_head_t * wait_address;
+};
+
 /*
  * Structures and helpers for sys_poll/sys_poll
  */
@@ -40,6 +55,8 @@ struct poll_wqueues {
         poll_table pt;
         struct poll_table_page * table;
         int error;
+        int inline_index;
+        struct poll_table_entry inline_entries[N_INLINE_POLL_ENTRIES];
 };
 
 extern void poll_initwait(struct poll_wqueues *pwq);