linux-ext4 - [PATCH v3 03/11] fs: only specify I_DIRTY_TIME when needed in generic_update

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Date:   Tue, 12 Jan 2021 11:02:45 -0800
From:   Eric Biggers <ebiggers@...nel.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     linux-xfs@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net,
        Theodore Ts'o <tytso@....edu>, Christoph Hellwig <hch@....de>,
        Jan Kara <jack@...e.cz>
Subject: [PATCH v3 03/11] fs: only specify I_DIRTY_TIME when needed in generic_update_time()

From: Eric Biggers <ebiggers@...gle.com>

generic_update_time() always passes I_DIRTY_TIME to
__mark_inode_dirty(), which doesn't really make sense because (a)
generic_update_time() might be asked to do only an i_version update, not
also a timestamps update; and (b) I_DIRTY_TIME is only supposed to be
set in i_state if the filesystem has lazytime enabled, so using it
unconditionally in generic_update_time() is inconsistent.

As a result there is a weird edge case where if only an i_version update
was requested (not also a timestamps update) but it is no longer needed
(i.e. inode_maybe_inc_iversion() returns false), then I_DIRTY_TIME will
be set in i_state even if the filesystem isn't mounted with lazytime.

Fix this by only passing I_DIRTY_TIME to __mark_inode_dirty() if the
timestamps were updated and the filesystem has lazytime enabled.

Reviewed-by: Christoph Hellwig <hch@....de>
Reviewed-by: Jan Kara <jack@...e.cz>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
---
 fs/inode.c | 38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 6442d97d9a4ab..d0fa43d8e9d5c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1743,24 +1743,26 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
 
 int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
 {
-	int iflags = I_DIRTY_TIME;
-	bool dirty = false;
-
-	if (flags & S_ATIME)
-		inode->i_atime = *time;
-	if (flags & S_VERSION)
-		dirty = inode_maybe_inc_iversion(inode, false);
-	if (flags & S_CTIME)
-		inode->i_ctime = *time;
-	if (flags & S_MTIME)
-		inode->i_mtime = *time;
-	if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
-	    !(inode->i_sb->s_flags & SB_LAZYTIME))
-		dirty = true;
-
-	if (dirty)
-		iflags |= I_DIRTY_SYNC;
-	__mark_inode_dirty(inode, iflags);
+	int dirty_flags = 0;
+
+	if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
+		if (flags & S_ATIME)
+			inode->i_atime = *time;
+		if (flags & S_CTIME)
+			inode->i_ctime = *time;
+		if (flags & S_MTIME)
+			inode->i_mtime = *time;
+
+		if (inode->i_sb->s_flags & SB_LAZYTIME)
+			dirty_flags |= I_DIRTY_TIME;
+		else
+			dirty_flags |= I_DIRTY_SYNC;
+	}
+
+	if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
+		dirty_flags |= I_DIRTY_SYNC;
+
+	__mark_inode_dirty(inode, dirty_flags);
 	return 0;
 }
 EXPORT_SYMBOL(generic_update_time);
-- 
2.30.0