overlayfs syncs all inode pages on sync_filesystem(), but it also
needs to call s_op->sync_fs() of upper fs for metadata sync.
This fixes correctness of syncfs(2) as demonstrated by following
xfs specific test:
xfs_sync_stats()
{
echo $1
echo -n "xfs_log_force = "
grep log /proc/fs/xfs/stat | awk '{ print $5 }'
}
xfs_sync_stats "before touch"
touch x
xfs_sync_stats "after touch"
xfs_io -c syncfs .
xfs_sync_stats "after syncfs"
xfs_io -c fsync x
xfs_sync_stats "after fsync"
xfs_io -c fsync x
xfs_sync_stats "after fsync #2"
When this test is run in overlay mount over xfs, log force
count does not increase with syncfs command.
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
fs/overlayfs/super.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
Miklos,
Re-posting this one proven bug fix detached from the overlay freeze series
that needs more work.
If you have some free cycles, I would love to get some feedback on
the change "vfs: freeze protect overlay inode on file_start_write()"
Thanks,
Amir.
v3:
- Added reviewed-by hch
- Detached from ovl freeze series
v2:
- Add test case to commit msg
v1:
- Same code as v3
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6792bb7..346f668 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -160,6 +160,25 @@ static void ovl_put_super(struct super_block *sb)
kfree(ufs);
}
+static int ovl_sync_fs(struct super_block *sb, int wait)
+{
+ struct ovl_fs *ufs = sb->s_fs_info;
+ struct super_block *upper_sb;
+ int ret;
+
+ if (!ufs->upper_mnt)
+ return 0;
+ upper_sb = ufs->upper_mnt->mnt_sb;
+ if (!upper_sb->s_op->sync_fs)
+ return 0;
+
+ /* real inodes have already been synced by sync_filesystem(ovl_sb) */
+ down_read(&upper_sb->s_umount);
+ ret = upper_sb->s_op->sync_fs(upper_sb, wait);
+ up_read(&upper_sb->s_umount);
+ return ret;
+}
+
/**
* ovl_statfs
* @sb: The overlayfs super block
@@ -222,6 +241,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
+ .sync_fs = ovl_sync_fs,
.statfs = ovl_statfs,
.show_options = ovl_show_options,
.remount_fs = ovl_remount,
--
2.7.4
--
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