4/10
----------------------------
commit cea86bf50d8d84c823e6f5feb6c6b31d813969e8
Author: Jaren Johnston <jaren's email>
Date: Fri Jun 8 15:48:56 2012 -0700
properly init sg in empty case
Change-Id: I7f2513a9a188cd3c2dd617200320f56b39704411
diff --git a/zc.c b/zc.c
index 77d31e5..ce929f0 100644
--- a/zc.c
+++ b/zc.c
@@ -53,25 +53,30 @@ int __get_userbuf(uint8_t __user *addr, uint32_t len,
int write,
int ret, pglen, i = 0;
struct scatterlist *sgp;
- down_write(&mm->mmap_sem);
- ret = get_user_pages(task, mm,
- (unsigned long)addr, pgcount,
write, 0, pg, NULL);
- up_write(&mm->mmap_sem);
- if (ret != pgcount)
- return -EINVAL;
+ if (unlikely(!pgcount || !len || !addr)) {
+ sg_mark_end(sg);
+ }
+ else {
+ down_write(&mm->mmap_sem);
+ ret = get_user_pages(task, mm,
+ (unsigned
long)addr, pgcount, write, 0, pg, NULL);
+ up_write(&mm->mmap_sem);
+ if (ret != pgcount)
+ return -EINVAL;
- sg_init_table(sg, pgcount);
+ sg_init_table(sg, pgcount);
- pglen = min((ptrdiff_t)(PAGE_SIZE - PAGEOFFSET(addr)),
(ptrdiff_t)len);
- sg_set_page(sg, pg[i++], pglen, PAGEOFFSET(addr));
+ pglen = min((ptrdiff_t)(PAGE_SIZE -
PAGEOFFSET(addr)), (ptrdiff_t)len);
+ sg_set_page(sg, pg[i++], pglen,
PAGEOFFSET(addr));
- len -= pglen;
- for (sgp = sg_next(sg); len; sgp = sg_next(sgp)) {
- pglen = min((uint32_t)PAGE_SIZE, len);
- sg_set_page(sgp, pg[i++], pglen, 0);
len -= pglen;
+ for (sgp = sg_next(sg); len; sgp =
sg_next(sgp)) {
+ pglen =
min((uint32_t)PAGE_SIZE, len);
+ sg_set_page(sgp, pg[i++],
pglen, 0);
+ len -= pglen;
+ }
+ sg_mark_end(sg_last(sg, pgcount));
}
- sg_mark_end(sg_last(sg, pgcount));
return 0;
}
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