diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index f98d40333c85..f67b956fb321 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -258,6 +258,56 @@ void __inode_attach_wb(struct inode *inode, struct page *page) wb_put(wb); } +/** + * locked_inode_to_wb_and_lock_list - determine a locked inode's wb and lock it + * @inode: inode of interest with i_lock held + * + * Returns @inode's wb with its list_lock held. @inode->i_lock must be + * held on entry and is released on return. The returned wb is guaranteed + * to stay @inode's associated wb until its list_lock is released. + */ +static struct bdi_writeback * +locked_inode_to_wb_and_lock_list(struct inode *inode) + __releases(&inode->i_lock) + __acquires(&wb->list_lock) +{ + while (true) { + struct bdi_writeback *wb = inode_to_wb(inode); + + /* + * inode_to_wb() association is protected by both + * @inode->i_lock and @wb->list_lock but list_lock nests + * outside i_lock. Drop i_lock and verify that the + * association hasn't changed after acquiring list_lock. + */ + wb_get(wb); + spin_unlock(&inode->i_lock); + spin_lock(&wb->list_lock); + wb_put(wb); /* not gonna deref it anymore */ + + if (likely(wb == inode_to_wb(inode))) + return wb; /* @inode already has ref */ + + spin_unlock(&wb->list_lock); + cpu_relax(); + spin_lock(&inode->i_lock); + } +} + +/** + * inode_to_wb_and_lock_list - determine an inode's wb and lock it + * @inode: inode of interest + * + * Same as locked_inode_to_wb_and_lock_list() but @inode->i_lock isn't held + * on entry. + */ +static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) + __acquires(&wb->list_lock) +{ + spin_lock(&inode->i_lock); + return locked_inode_to_wb_and_lock_list(inode); +} + /** * wbc_attach_and_unlock_inode - associate wbc with target inode and unlock it * @wbc: writeback_control of interest @@ -603,6 +653,27 @@ restart: #else /* CONFIG_CGROUP_WRITEBACK */ +static struct bdi_writeback * +locked_inode_to_wb_and_lock_list(struct inode *inode) + __releases(&inode->i_lock) + __acquires(&wb->list_lock) +{ + struct bdi_writeback *wb = inode_to_wb(inode); + + spin_unlock(&inode->i_lock); + spin_lock(&wb->list_lock); + return wb; +} + +static struct bdi_writeback *inode_to_wb_and_lock_list(struct inode *inode) + __acquires(&wb->list_lock) +{ + struct bdi_writeback *wb = inode_to_wb(inode); + + spin_lock(&wb->list_lock); + return wb; +} + static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages) { return nr_pages; @@ -678,9 +749,9 @@ void wb_start_background_writeback(struct bdi_writeback *wb) */ void inode_wb_list_del(struct inode *inode) { - struct bdi_writeback *wb = inode_to_wb(inode); + struct bdi_writeback *wb; - spin_lock(&wb->list_lock); + wb = inode_to_wb_and_lock_list(inode); inode_wb_list_del_locked(inode, wb); spin_unlock(&wb->list_lock); } @@ -1784,12 +1855,11 @@ void __mark_inode_dirty(struct inode *inode, int flags) * reposition it (that would break b_dirty time-ordering). */ if (!was_dirty) { - struct bdi_writeback *wb = inode_to_wb(inode); + struct bdi_writeback *wb; struct list_head *dirty_list; bool wakeup_bdi = false; - spin_unlock(&inode->i_lock); - spin_lock(&wb->list_lock); + wb = locked_inode_to_wb_and_lock_list(inode); WARN(bdi_cap_writeback_dirty(wb->bdi) && !test_bit(WB_registered, &wb->state),