linux-kernel - [PATCH v2] ext4: fix the time handling macros when ext4 is using small inodes

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Message-Id: <20230719-ctime-v2-1-869825696d6d@kernel.org>
Date:   Wed, 19 Jul 2023 06:32:19 -0400
From:   Jeff Layton <jlayton@...nel.org>
To:     Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Christian Brauner <brauner@...nel.org>
Cc:     linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>
Subject: [PATCH v2] ext4: fix the time handling macros when ext4 is using
 small inodes

If ext4 is using small on-disk inodes, then it may not be able to store
fine grained timestamps. It also can't store the i_crtime at all in that
case since that fully lives in the extended part of the inode.

979492850abd got the EXT4_EINODE_{GET,SET}_XTIME macros wrong, and would
still store the tv_sec field of the i_crtime into the raw_inode, even
when they were small, corrupting adjacent memory.

This fixes those macros to skip setting anything in the raw_inode if the
tv_sec field doesn't fit, and to properly return a {0,0} timestamp when
the raw_inode doesn't support it.

Also, fix a bug in ctime handling during rename. It was updating the
renamed inode's ctime twice rather than the old directory.

Cc: Jan Kara <jack@...e.cz>
Fixes: 979492850abd ("ext4: convert to ctime accessor functions")
Reported-by: Hugh Dickins <hughd@...gle.com>
Tested-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Jeff Layton <jlayton@...nel.org>
---
Changes in v2:
- also fix incorrect ctime update in ext4_rename
---
 fs/ext4/ext4.h  | 17 ++++++++++++-----
 fs/ext4/namei.c |  2 +-
 2 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 2af347669db7..1e2259d9967d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -900,8 +900,10 @@ do {										\
 #define EXT4_INODE_SET_CTIME(inode, raw_inode)					\
 	EXT4_INODE_SET_XTIME_VAL(i_ctime, inode, raw_inode, inode_get_ctime(inode))
 
-#define EXT4_EINODE_SET_XTIME(xtime, einode, raw_inode)			       \
-	EXT4_INODE_SET_XTIME_VAL(xtime, &((einode)->vfs_inode), raw_inode, (einode)->xtime)
+#define EXT4_EINODE_SET_XTIME(xtime, einode, raw_inode)				\
+	if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime))			\
+		EXT4_INODE_SET_XTIME_VAL(xtime, &((einode)->vfs_inode),		\
+					 raw_inode, (einode)->xtime)
 
 #define EXT4_INODE_GET_XTIME_VAL(xtime, inode, raw_inode)			\
 	(EXT4_FITS_IN_INODE(raw_inode, EXT4_I(inode), xtime ## _extra) ?	\
@@ -922,9 +924,14 @@ do {										\
 		EXT4_INODE_GET_XTIME_VAL(i_ctime, inode, raw_inode));		\
 } while (0)
 
-#define EXT4_EINODE_GET_XTIME(xtime, einode, raw_inode)			       \
-do {									       \
-	(einode)->xtime = EXT4_INODE_GET_XTIME_VAL(xtime, &(einode->vfs_inode), raw_inode);	\
+#define EXT4_EINODE_GET_XTIME(xtime, einode, raw_inode)				\
+do {										\
+	if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime)) 			\
+		(einode)->xtime =						\
+			EXT4_INODE_GET_XTIME_VAL(xtime, &(einode->vfs_inode),	\
+						 raw_inode);			\
+	else									\
+		(einode)->xtime = (struct timespec64){0, 0};			\
 } while (0)
 
 #define i_disk_version osd1.linux1.l_i_version
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 07f6d96ebc60..933ad03f4f58 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3957,7 +3957,7 @@ static int ext4_rename(struct mnt_idmap *idmap, struct inode *old_dir,
 		ext4_dec_count(new.inode);
 		inode_set_ctime_current(new.inode);
 	}
-	old.dir->i_mtime = inode_set_ctime_current(old.inode);
+	old.dir->i_mtime = inode_set_ctime_current(old.dir);
 	ext4_update_dx_flag(old.dir);
 	if (old.dir_bh) {
 		retval = ext4_rename_dir_finish(handle, &old, new.dir->i_ino);

---
base-commit: c62e19541f8bb39f1f340247f651afe4532243df
change-id: 20230718-ctime-f140dae8789d

Best regards,
-- 
Jeff Layton <jlayton@...nel.org>