From 0568b409c74f7a125d92a09a3f386785700ef688 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 1 May 2006 19:50:48 +0200 Subject: [PATCH] [PATCH] splice: fix bugs in pipe_to_file() Found by Oleg Nesterov , 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 --- fs/pipe.c | 3 --- fs/splice.c | 37 +++++++++++++++++++------------------ include/linux/pipe_fs_i.h | 3 +-- 3 files changed, 20 insertions(+), 23 deletions(-) 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 @@ 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; } 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 @@ 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); 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; -- 1.8.2.3