From dd73e4b7df9589fa603fc6d128b4f6cabb250e8e Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 16 Jun 2015 18:48:30 -0400 Subject: [PATCH] writeback: do foreign inode detection iff cgroup writeback is enabled 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 Signed-off-by: Jens Axboe --- fs/fs-writeback.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c index f60de54d2042..f0520bcf2094 100644 --- a/fs/fs-writeback.c +++ b/fs/fs-writeback.c @@ -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) {