@@ -596,10 +596,18 @@ void wbc_account_io(struct writeback_control *wbc, struct page *page,
*/
int inode_congested(struct inode *inode, int cong_bits)
{
- if (inode) {
- struct bdi_writeback *wb = inode_to_wb(inode);
- if (wb)
- return wb_congested(wb, cong_bits);
+ /*
+ * Once set, ->i_wb never becomes NULL while the inode is alive.
+ * Start transaction iff ->i_wb is visible.
+ */
+ if (inode && inode_to_wb(inode)) {
+ struct bdi_writeback *wb;
+ bool locked, congested;
+
+ wb = unlocked_inode_to_wb_begin(inode, &locked);
+ congested = wb_congested(wb, cong_bits);
+ unlocked_inode_to_wb_end(inode, locked);
+ return congested;
}
return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
Similar to wb stat updates, inode_congested() accesses the associated wb of an inode locklessly, which will break with foreign inode wb switching. This path updates inode_congested() to use unlocked inode wb access transaction introduced by the previous patch. Combined with the previous two patches, this makes all wb list and access operations to be protected by either of inode->i_lock, wb->list_lock, or mapping->tree_lock while wb switching is in progress. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jens Axboe <axboe@kernel.dk> Cc: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: Greg Thelen <gthelen@google.com> --- fs/fs-writeback.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-)