[PATCH] splice: fix bugs in pipe_to_file()
Found by Oleg Nesterov <oleg@tv-sign.ru>, fixed by me.
- Only allow full pages to go to the page cache.
- Check page != buf->page instead of using PIPE_BUF_FLAG_STOLEN.
- Remember to clear 'stolen' if add_to_page_cache() fails.
And as a cleanup on that:
- Make the bottom fall-through logic a little less convoluted. Also make
the steal path hold an extra reference to the page, so we don't have
to differentiate between stolen and non-stolen at the end.
Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/fs/pipe.c b/fs/pipe.c
index 5a36927..888f265 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -99,8 +99,6 @@
{
struct page *page = buf->page;
- buf->flags &= ~PIPE_BUF_FLAG_STOLEN;
-
/*
* If nobody else uses this page, and we don't already have a
* temporary page, let's keep track of it as a one-deep
@@ -130,7 +128,6 @@
struct page *page = buf->page;
if (page_count(page) == 1) {
- buf->flags |= PIPE_BUF_FLAG_STOLEN;
lock_page(page);
return 0;
}
diff --git a/fs/splice.c b/fs/splice.c
index 9df28d3..1633778 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -78,7 +78,7 @@
return 1;
}
- buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
+ buf->flags |= PIPE_BUF_FLAG_LRU;
return 0;
}
@@ -87,7 +87,7 @@
{
page_cache_release(buf->page);
buf->page = NULL;
- buf->flags &= ~(PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU);
+ buf->flags &= ~PIPE_BUF_FLAG_LRU;
}
static void *page_cache_pipe_buf_map(struct file *file,
@@ -587,9 +587,10 @@
this_len = PAGE_CACHE_SIZE - offset;
/*
- * Reuse buf page, if SPLICE_F_MOVE is set.
+ * Reuse buf page, if SPLICE_F_MOVE is set and we are doing a full
+ * page.
*/
- if (sd->flags & SPLICE_F_MOVE) {
+ if ((sd->flags & SPLICE_F_MOVE) && this_len == PAGE_CACHE_SIZE) {
/*
* If steal succeeds, buf->page is now pruned from the vm
* side (LRU and page cache) and we can reuse it. The page
@@ -604,6 +605,8 @@
goto find_page;
}
+ page_cache_get(page);
+
if (!(buf->flags & PIPE_BUF_FLAG_LRU))
lru_cache_add(page);
} else {
@@ -662,7 +665,7 @@
} else if (ret)
goto out;
- if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
+ if (buf->page != page) {
char *dst = kmap_atomic(page, KM_USER0);
memcpy(dst + offset, src + buf->offset, this_len);
@@ -671,22 +674,20 @@
}
ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
- if (ret == AOP_TRUNCATED_PAGE) {
+ if (!ret) {
+ /*
+ * Return the number of bytes written and mark page as
+ * accessed, we are now done!
+ */
+ ret = this_len;
+ mark_page_accessed(page);
+ balance_dirty_pages_ratelimited(mapping);
+ } else if (ret == AOP_TRUNCATED_PAGE) {
page_cache_release(page);
goto find_page;
- } else if (ret)
- goto out;
-
- /*
- * Return the number of bytes written.
- */
- ret = this_len;
- mark_page_accessed(page);
- balance_dirty_pages_ratelimited(mapping);
+ }
out:
- if (!(buf->flags & PIPE_BUF_FLAG_STOLEN))
- page_cache_release(page);
-
+ page_cache_release(page);
unlock_page(page);
out_nomem:
buf->ops->unmap(info, buf);
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 0008d4b..3130977 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -5,8 +5,7 @@
#define PIPE_BUFFERS (16)
-#define PIPE_BUF_FLAG_STOLEN 0x01
-#define PIPE_BUF_FLAG_LRU 0x02
+#define PIPE_BUF_FLAG_LRU 0x01
struct pipe_buffer {
struct page *page;