[PATCH 4.19.y] erofs: derive atime instead of leaving it empty

[Greg KH]

On Tue, Nov 17, 2020 at 12:47:37AM +0800, Gao Xiang wrote:
> From: Gao Xiang <hsiangkao at redhat.com>
> 
> commit d3938ee23e97bfcac2e0eb6b356875da73d700df upstream.
> 
> EROFS has _only one_ ondisk timestamp (ctime is currently
> documented and recorded, we might also record mtime instead
> with a new compat feature if needed) for each extended inode
> since EROFS isn't mainly for archival purposes so no need to
> keep all timestamps on disk especially for Android scenarios
> due to security concerns. Also, romfs/cramfs don't have their
> own on-disk timestamp, and squashfs only records mtime instead.
> 
> Let's also derive access time from ondisk timestamp rather than
> leaving it empty, and if mtime/atime for each file are really
> needed for specific scenarios as well, we can also use xattrs
> to record them then.
> 
> Link: https://lore.kernel.org/r/20201031195102.21221-1-hsiangkao@aol.com
> [ Gao Xiang: It'd be better to backport for user-friendly concern. ]
> Fixes: 431339ba9042 ("staging: erofs: add inode operations")
> Cc: stable <stable at vger.kernel.org> # 4.19+
> Reported-by: nl6720 <nl6720 at gmail.com>
> Reviewed-by: Chao Yu <yuchao0 at huawei.com>
> [ Gao Xiang: Manually backport to 4.19.y due to trivial conflicts. ]
> Signed-off-by: Gao Xiang <hsiangkao at redhat.com>
> ---
>  drivers/staging/erofs/inode.c | 21 +++++++++++----------
>  1 file changed, 11 insertions(+), 10 deletions(-)

Now queued up, thanks for the backport!

greg k-h