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[PATCH] splice: fix bugs in pipe_to_file()

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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>
This commit is contained in:
Jens Axboe 2006-05-01 19:50:48 +02:00
parent 46e678c96b
commit 0568b409c7
3 changed files with 20 additions and 23 deletions
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3
fs/pipe.c
View file

@ -99,8 +99,6 @@ static void anon_pipe_buf_release(struct pipe_inode_info *pipe,
{
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 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
struct page *page = buf->page;
if (page_count(page) == 1) {
buf->flags |= PIPE_BUF_FLAG_STOLEN;
lock_page(page);
return 0;
}

37
fs/splice.c
View file

@ -78,7 +78,7 @@ static int page_cache_pipe_buf_steal(struct pipe_inode_info *info,
return 1;
}
buf->flags |= PIPE_BUF_FLAG_STOLEN | PIPE_BUF_FLAG_LRU;
buf->flags |= PIPE_BUF_FLAG_LRU;
return 0;
}
@ -87,7 +87,7 @@ static void page_cache_pipe_buf_release(struct pipe_inode_info *info,
{
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 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
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 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
goto find_page;
}
page_cache_get(page);
if (!(buf->flags & PIPE_BUF_FLAG_LRU))
lru_cache_add(page);
} else {
@ -662,7 +665,7 @@ find_page:
} 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 @@ find_page:
}
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);

3
include/linux/pipe_fs_i.h
View file

@ -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;