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authorMel Gorman <mel@csn.ul.ie>2010-03-02 22:24:19 +0000
committerGreg Kroah-Hartman <gregkh@suse.de>2010-04-01 15:58:31 -0700
commitd640f45411308c70e205d04938dfda94152738fb (patch)
treed1ee2a3943ef00b6c454c45c70ad1b0da792468e /include/linux/tty.h
parentd560f99c9aafb9ebe1911541cf30d909819564eb (diff)
tty: Take a 256 byte padding into account when buffering below sub-page units
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>
Diffstat (limited to 'include/linux/tty.h')
-rw-r--r--include/linux/tty.h9
1 files changed, 5 insertions, 4 deletions
diff --git a/include/linux/tty.h b/include/linux/tty.h
index c396b449f77e..e9c57e9bb7f2 100644
--- 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 {