From: "Martin J. Bligh" <mbligh@aracnet.com>
This was to fix the issue you had with boehm-gc & 4/4 split.
mm/usercopy.c | 40 +++++++++++++++++++++++++++-------------
1 files changed, 27 insertions(+), 13 deletions(-)
diff -puN mm/usercopy.c~4g4g-locked-userspace-copy mm/usercopy.c
--- 25/mm/usercopy.c~4g4g-locked-userspace-copy 2003-12-25 00:36:06.000000000 -0800
+++ 25-akpm/mm/usercopy.c 2003-12-25 00:36:06.000000000 -0800
@@ -30,21 +30,22 @@ static inline struct page *pin_page(unsi
struct page *page = NULL;
int ret;
- spin_lock(&mm->page_table_lock);
/*
* Do a quick atomic lookup first - this is the fastpath.
*/
+retry:
page = follow_page(mm, addr, write);
if (likely(page != NULL)) {
if (!PageReserved(page))
get_page(page);
- spin_unlock(&mm->page_table_lock);
return page;
}
/*
* No luck - bad address or need to fault in the page:
*/
+
+ /* Release the lock so get_user_pages can sleep */
spin_unlock(&mm->page_table_lock);
/*
@@ -53,15 +54,23 @@ static inline struct page *pin_page(unsi
* filemap_copy_from_user() to recover: drop its atomic kmap and use
* a sleeping kmap instead.
*/
- if (in_atomic())
+ if (in_atomic()) {
+ spin_lock(&mm->page_table_lock);
return NULL;
+ }
down_read(&mm->mmap_sem);
- ret = get_user_pages(current, mm, addr, 1, write, 0, &page, NULL);
+ ret = get_user_pages(current, mm, addr, 1, write, 0, NULL, NULL);
up_read(&mm->mmap_sem);
+ spin_lock(&mm->page_table_lock);
+
if (ret <= 0)
return NULL;
- return page;
+
+ /*
+ * Go try the follow_page again.
+ */
+ goto retry;
}
static inline void unpin_page(struct page *page)
@@ -76,9 +85,13 @@ static inline void unpin_page(struct pag
*/
static int rw_vm(unsigned long addr, void *buf, int len, int write)
{
+ struct mm_struct *mm = current->mm ? : &init_mm;
+
if (!len)
return 0;
+ spin_lock(&mm->page_table_lock);
+
/* ignore errors, just check how much was sucessfully transfered */
while (len) {
struct page *page = NULL;
@@ -126,6 +139,7 @@ static int rw_vm(unsigned long addr, voi
buf += bytes;
addr += bytes;
}
+ spin_unlock(&mm->page_table_lock);
return len;
}
@@ -139,18 +153,18 @@ static int str_vm(unsigned long addr, vo
if (!len)
return len;
- down_read(&mm->mmap_sem);
+ spin_lock(&mm->page_table_lock);
+
/* ignore errors, just check how much was sucessfully transfered */
while (len) {
- int bytes, ret, offset, left, copied;
+ int bytes, offset, left, copied;
char *maddr;
- ret = get_user_pages(current, mm, addr, 1, copy == 2, 0, &page, NULL);
- if (ret <= 0) {
- up_read(&mm->mmap_sem);
+ page = pin_page(addr, copy == 2);
+ if (!page) {
+ spin_unlock(&mm->page_table_lock);
return -EFAULT;
}
-
bytes = len;
offset = addr & (PAGE_SIZE-1);
if (bytes > PAGE_SIZE-offset)
@@ -170,14 +184,14 @@ static int str_vm(unsigned long addr, vo
}
BUG_ON(bytes < 0 || copied < 0);
kunmap_atomic(maddr, KM_USER_COPY);
- page_cache_release(page);
+ unpin_page(page);
len -= copied;
buf += copied;
addr += copied;
if (left)
break;
}
- up_read(&mm->mmap_sem);
+ spin_unlock(&mm->page_table_lock);
return len;
}
_