writeback: do foreign inode detection iff cgroup writeback is enabled (dd73e4b7) · Commits · 戴 / test

Currently, even when a filesystem doesn't set the FS_CGROUP_WRITEBACK flag, if the filesystem uses wbc_init_bio() and wbc_account_io(), the foreign inode detection and migration logic still ends up activating cgroup writeback which is unexpected. This patch ensures that the foreign inode detection logic stays disabled when inode_cgwb_enabled() is false by not associating writeback_control's with bdi_writeback's. This also avoids unnecessary operations in wbc_init_bio(), wbc_account_io() and wbc_detach_inode() for filesystems which don't support cgroup writeback. Signed-off-by:

Tejun Heo <tj@kernel.org> Signed-off-by:

Jens Axboe <axboe@fb.com>

fs/fs-writeback.c

+13 −3

Original line number	Diff line number	Diff line
		@@ -513,6 +513,11 @@ out_free:
		void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
		struct inode *inode)
		{
		if (!inode_cgwb_enabled(inode)) {
		spin_unlock(&inode->i_lock);
		return;
		}

		wbc->wb = inode_to_wb(inode);
		wbc->inode = inode;

		@@ -575,11 +580,16 @@ void wbc_detach_inode(struct writeback_control *wbc)
		{
		struct bdi_writeback *wb = wbc->wb;
		struct inode *inode = wbc->inode;
		u16 history = inode->i_wb_frn_history;
		unsigned long avg_time = inode->i_wb_frn_avg_time;
		unsigned long max_bytes, max_time;
		unsigned long avg_time, max_bytes, max_time;
		u16 history;
		int max_id;

		if (!wb)
		return;

		history = inode->i_wb_frn_history;
		avg_time = inode->i_wb_frn_avg_time;

		/* pick the winner of this round */
		if (wbc->wb_bytes >= wbc->wb_lcand_bytes &&
		wbc->wb_bytes >= wbc->wb_tcand_bytes) {

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