From c146024ec44c2946de7c6c45ddd3402abcab17f9 Mon Sep 17 00:00:00 2001 From: Miklos Szeredi Date: Tue, 14 Jul 2020 14:45:41 +0200 Subject: fuse: fix warning in tree_insert() and clean up writepage insertion fuse_writepages_fill() calls tree_insert() with ap->num_pages = 0 which triggers the following warning: WARNING: CPU: 1 PID: 17211 at fs/fuse/file.c:1728 tree_insert+0xab/0xc0 [fuse] RIP: 0010:tree_insert+0xab/0xc0 [fuse] Call Trace: fuse_writepages_fill+0x5da/0x6a0 [fuse] write_cache_pages+0x171/0x470 fuse_writepages+0x8a/0x100 [fuse] do_writepages+0x43/0xe0 Fix up the warning and clean up the code around rb-tree insertion: - Rename tree_insert() to fuse_insert_writeback() and make it return the conflicting entry in case of failure - Re-add tree_insert() as a wrapper around fuse_insert_writeback() - Rename fuse_writepage_in_flight() to fuse_writepage_add() and reverse the meaning of the return value to mean + "true" in case the writepage entry was successfully added + "false" in case it was in-fligt queued on an existing writepage entry's auxiliary list or the existing writepage entry's temporary page updated Switch from fuse_find_writeback() + tree_insert() to fuse_insert_writeback() - Move setting orig_pages to before inserting/updating the entry; this may result in the orig_pages value being discarded later in case of an in-flight request - In case of a new writepage entry use fuse_writepage_add() unconditionally, only set data->wpa if the entry was added. Fixes: 6b2fb79963fb ("fuse: optimize writepages search") Reported-by: kernel test robot Original-path-by: Vasily Averin Signed-off-by: Miklos Szeredi --- fs/fuse/file.c | 62 ++++++++++++++++++++++++++++------------------------------ 1 file changed, 30 insertions(+), 32 deletions(-) (limited to 'fs') diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 7247c02adb32..63d52fed3381 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1674,7 +1674,8 @@ __acquires(fi->lock) } } -static void tree_insert(struct rb_root *root, struct fuse_writepage_args *wpa) +static struct fuse_writepage_args *fuse_insert_writeback(struct rb_root *root, + struct fuse_writepage_args *wpa) { pgoff_t idx_from = wpa->ia.write.in.offset >> PAGE_SHIFT; pgoff_t idx_to = idx_from + wpa->ia.ap.num_pages - 1; @@ -1697,11 +1698,17 @@ static void tree_insert(struct rb_root *root, struct fuse_writepage_args *wpa) else if (idx_to < curr_index) p = &(*p)->rb_left; else - return (void) WARN_ON(true); + return curr; } rb_link_node(&wpa->writepages_entry, parent, p); rb_insert_color(&wpa->writepages_entry, root); + return NULL; +} + +static void tree_insert(struct rb_root *root, struct fuse_writepage_args *wpa) +{ + WARN_ON(fuse_insert_writeback(root, wpa)); } static void fuse_writepage_end(struct fuse_conn *fc, struct fuse_args *args, @@ -1953,14 +1960,14 @@ static void fuse_writepages_send(struct fuse_fill_wb_data *data) } /* - * First recheck under fi->lock if the offending offset is still under - * writeback. If yes, then iterate auxiliary write requests, to see if there's + * Check under fi->lock if the page is under writeback, and insert it onto the + * rb_tree if not. Otherwise iterate auxiliary write requests, to see if there's * one already added for a page at this offset. If there's none, then insert * this new request onto the auxiliary list, otherwise reuse the existing one by - * copying the new page contents over to the old temporary page. + * swapping the new temp page with the old one. */ -static bool fuse_writepage_in_flight(struct fuse_writepage_args *new_wpa, - struct page *page) +static bool fuse_writepage_add(struct fuse_writepage_args *new_wpa, + struct page *page) { struct fuse_inode *fi = get_fuse_inode(new_wpa->inode); struct fuse_writepage_args *tmp; @@ -1968,17 +1975,15 @@ static bool fuse_writepage_in_flight(struct fuse_writepage_args *new_wpa, struct fuse_args_pages *new_ap = &new_wpa->ia.ap; WARN_ON(new_ap->num_pages != 0); + new_ap->num_pages = 1; spin_lock(&fi->lock); - rb_erase(&new_wpa->writepages_entry, &fi->writepages); - old_wpa = fuse_find_writeback(fi, page->index, page->index); + old_wpa = fuse_insert_writeback(&fi->writepages, new_wpa); if (!old_wpa) { - tree_insert(&fi->writepages, new_wpa); spin_unlock(&fi->lock); - return false; + return true; } - new_ap->num_pages = 1; for (tmp = old_wpa->next; tmp; tmp = tmp->next) { pgoff_t curr_index; @@ -2007,7 +2012,7 @@ static bool fuse_writepage_in_flight(struct fuse_writepage_args *new_wpa, fuse_writepage_free(new_wpa); } - return true; + return false; } static int fuse_writepages_fill(struct page *page, @@ -2086,12 +2091,6 @@ static int fuse_writepages_fill(struct page *page, ap->args.end = fuse_writepage_end; ap->num_pages = 0; wpa->inode = inode; - - spin_lock(&fi->lock); - tree_insert(&fi->writepages, wpa); - spin_unlock(&fi->lock); - - data->wpa = wpa; } set_page_writeback(page); @@ -2099,26 +2098,25 @@ static int fuse_writepages_fill(struct page *page, ap->pages[ap->num_pages] = tmp_page; ap->descs[ap->num_pages].offset = 0; ap->descs[ap->num_pages].length = PAGE_SIZE; + data->orig_pages[ap->num_pages] = page; inc_wb_stat(&inode_to_bdi(inode)->wb, WB_WRITEBACK); inc_node_page_state(tmp_page, NR_WRITEBACK_TEMP); err = 0; - if (is_writeback && fuse_writepage_in_flight(wpa, page)) { + if (data->wpa) { + /* + * Protected by fi->lock against concurrent access by + * fuse_page_is_writeback(). + */ + spin_lock(&fi->lock); + ap->num_pages++; + spin_unlock(&fi->lock); + } else if (fuse_writepage_add(wpa, page)) { + data->wpa = wpa; + } else { end_page_writeback(page); - data->wpa = NULL; - goto out_unlock; } - data->orig_pages[ap->num_pages] = page; - - /* - * Protected by fi->lock against concurrent access by - * fuse_page_is_writeback(). - */ - spin_lock(&fi->lock); - ap->num_pages++; - spin_unlock(&fi->lock); - out_unlock: unlock_page(page); -- cgit