| Date | Tue, 30 Mar 2010 15:55:40 -0700 | From | Greg KH <> | Subject | [062/116] tty: Take a 256 byte padding into account when buffering below sub-page units |
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2.6.32-stable review patch. If anyone has any objections, please let us know.
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From: Mel Gorman <mel@csn.ul.ie>
commit 352fa6ad16b89f8ffd1a93b4419b1a8f2259feab upstream.
The TTY layer takes some care to ensure that only sub-page allocations are made with interrupts disabled. It does this by setting a goal of "TTY_BUFFER_PAGE" to allocate. Unfortunately, while TTY_BUFFER_PAGE takes the size of tty_buffer into account, it fails to account that tty_buffer_find() rounds the buffer size out to the next 256 byte boundary before adding on the size of the tty_buffer.
This patch adjusts the TTY_BUFFER_PAGE calculation to take into account the size of the tty_buffer and the padding. Once applied, tty_buffer_alloc() should not require high-order allocations.
Signed-off-by: Mel Gorman <mel@csn.ul.ie> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- include/linux/tty.h | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
--- a/include/linux/tty.h +++ b/include/linux/tty.h @@ -70,12 +70,13 @@ struct tty_buffer { /* * We default to dicing tty buffer allocations to this many characters - * in order to avoid multiple page allocations. We assume tty_buffer itself - * is under 256 bytes. See tty_buffer_find for the allocation logic this - * must match + * in order to avoid multiple page allocations. We know the size of + * tty_buffer itself but it must also be taken into account that the + * the buffer is 256 byte aligned. See tty_buffer_find for the allocation + * logic this must match */ -#define TTY_BUFFER_PAGE ((PAGE_SIZE - 256) / 2) +#define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF) struct tty_bufhead {
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