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authorBadari Pulavarty <pbadari@us.ibm.com>2007-05-23 13:57:45 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-23 20:14:12 -0700
commit6087b2dab2c914268b1a50882edbbad82bfefd29 (patch)
tree3f286422a61e7e3206b4a0dba6cb7c18a09e6463 /fs
parent7bb44adef39ad3bda2be40bb34686bc56bd563a5 (diff)
optimize compat_core_sys_select() by a using stack space for small fd sets
Optimize select by a using stack space for small fd sets. core_sys_select() already has this optimization. This is for compat version. Signed-off-by: Badari Pulavarty <pbadari@us.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/compat.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/fs/compat.c b/fs/compat.c
index 1de2331db84..4db6216e526 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1544,9 +1544,10 @@ int compat_core_sys_select(int n, compat_ulong_t __user *inp,
compat_ulong_t __user *outp, compat_ulong_t __user *exp, s64 *timeout)
{
fd_set_bits fds;
- char *bits;
+ void *bits;
int size, max_fds, ret = -EINVAL;
struct fdtable *fdt;
+ long stack_fds[SELECT_STACK_ALLOC/sizeof(long)];
if (n < 0)
goto out_nofds;
@@ -1564,11 +1565,14 @@ int compat_core_sys_select(int n, compat_ulong_t __user *inp,
* since we used fdset we need to allocate memory in units of
* long-words.
*/
- ret = -ENOMEM;
size = FDS_BYTES(n);
- bits = kmalloc(6 * size, GFP_KERNEL);
- if (!bits)
- goto out_nofds;
+ bits = stack_fds;
+ if (size > sizeof(stack_fds) / 6) {
+ bits = kmalloc(6 * size, GFP_KERNEL);
+ ret = -ENOMEM;
+ if (!bits)
+ goto out_nofds;
+ }
fds.in = (unsigned long *) bits;
fds.out = (unsigned long *) (bits + size);
fds.ex = (unsigned long *) (bits + 2*size);
@@ -1600,7 +1604,8 @@ int compat_core_sys_select(int n, compat_ulong_t __user *inp,
compat_set_fd_set(n, exp, fds.res_ex))
ret = -EFAULT;
out:
- kfree(bits);
+ if (bits != stack_fds)
+ kfree(bits);
out_nofds:
return ret;
}