FAILED: patch "[PATCH] fs: fix lazytime expiration handling in" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1e249cb5b7fc09ff216aa5a12f6c302e434e88f9 Mon Sep 17 00:00:00 2001
From: Eric Biggers <[email protected]>
Date: Tue, 12 Jan 2021 11:02:43 -0800
Subject: [PATCH] fs: fix lazytime expiration handling in
__writeback_single_inode()

When lazytime is enabled and an inode is being written due to its in-memory updated timestamps having expired, either due to a sync() or syncfs() system call or due to dirtytime_expire_interval having elapsed, the VFS needs to inform the filesystem so that the filesystem can copy the inode's timestamps out to the on-disk data structures.

This is done by __writeback_single_inode() calling mark_inode_dirty_sync(), which then calls ->dirty_inode(I_DIRTY_SYNC).

However, this occurs after __writeback_single_inode() has already cleared the dirty flags from ->i_state. This causes two bugs:

- mark_inode_dirty_sync() redirties the inode, causing it to remain dirty. This wastefully causes the inode to be written twice. But more importantly, it breaks cases where sync_filesystem() is expected to clean dirty inodes. This includes the FS_IOC_REMOVE_ENCRYPTION_KEY ioctl (as reported at
https://lore.kernel.org/r/[email protected]), as well as possibly filesystem freezing (freeze_super()).

- Since ->i_state doesn't contain I_DIRTY_TIME when ->dirty_inode() is called from __writeback_single_inode() for lazytime expiration, xfs_fs_dirty_inode() ignores the notification. (XFS only cares about lazytime expirations, and it assumes that i_state will contain I_DIRTY_TIME during those.) Therefore, lazy timestamps aren't persisted by sync(), syncfs(), or dirtytime_expire_interval on XFS.

Fix this by moving the call to mark_inode_dirty_sync() to earlier in __writeback_single_inode(), before the dirty flags are cleared from i_state. This makes filesystems be properly notified of the timestamp expiration, and it avoids incorrectly redirtying the inode.

This fixes xfstest generic/580 (which tests FS_IOC_REMOVE_ENCRYPTION_KEY) when run on ext4 or f2fs with lazytime enabled. It also fixes the new lazytime xfstest I've proposed, which reproduces the above-mentioned XFS bug
(https://lore.kernel.org/r/[email protected]).

Alternatively, we could call ->dirty_inode(I_DIRTY_SYNC) directly. But due to the introduction of I_SYNC_QUEUED, mark_inode_dirty_sync() is the right thing to do because mark_inode_dirty_sync() now knows not to move the inode to a writeback list if it is currently queued for sync.

Depends-on: 5afced3bf281 ("writeback: Avoid skipping inode writeback")

index acfb55834af2..c41cb887eb7d 100644
@@ -1474,21 +1474,25 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 	}
 
 	/*
-	 * Some filesystems may redirty the inode during the writeback
-	 * due to delalloc, clear dirty metadata flags right before
-	 * write_inode()
+	 * If the inode has dirty timestamps and we need to write them, call
+	 * mark_inode_dirty_sync() to notify the filesystem about it and to
+	 * change I_DIRTY_TIME into I_DIRTY_SYNC.
 	 */
-	spin_lock(&inode->i_lock);
-
-	dirty = inode->i_state & I_DIRTY;
 	if ((inode->i_state & I_DIRTY_TIME) &&
-	    ((dirty & I_DIRTY_INODE) ||
-	     wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
+	    (wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
 	     time_after(jiffies, inode->dirtied_time_when +
 			dirtytime_expire_interval * HZ))) {
-		dirty |= I_DIRTY_TIME;
 		trace_writeback_lazytime(inode);
+		mark_inode_dirty_sync(inode);
 	}
+
+	/*
+	 * Some filesystems may redirty the inode during the writeback
+	 * due to delalloc, clear dirty metadata flags right before
+	 * write_inode()
+	 */
+	spin_lock(&inode->i_lock);
+	dirty = inode->i_state & I_DIRTY;
 	inode->i_state &= ~dirty;
 
 	/*

@@ -1509,8 +1513,6 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 
 	spin_unlock(&inode->i_lock);
 
-	if (dirty & I_DIRTY_TIME)
-		mark_inode_dirty_sync(inode);
 	/* Don't write the inode if only I_DIRTY_PAGES was set */
 	if (dirty & ~I_DIRTY_PAGES) {
 		int err = write_inode(inode, wbc);