On Fri, Sep 10, 2021 at 3:17 AM Sasha Levin sashal@kernel.org wrote:
From: Amir Goldstein amir73il@gmail.com
[ Upstream commit 72db82115d2bdfbfba8b15a92d91872cfe1b40c6 ]
When a lower file has sync/noatime fileattr flags, the behavior of overlayfs post copy up is inconsistent.
Immediately after copy up, ovl inode still has the S_SYNC/S_NOATIME inode flags copied from lower inode, so vfs code still treats the ovl inode as sync/noatime. After ovl inode evict or mount cycle, the ovl inode does not have these inode flags anymore.
To fix this inconsistency, try to copy the fileattr flags on copy up if the upper fs supports the fileattr_set() method.
This gives consistent behavior post copy up regardless of inode eviction from cache.
We cannot copy up the immutable/append-only inode flags in a similar manner, because immutable/append-only inodes cannot be linked and because overlayfs will not be able to set overlay.* xattr on the upper inodes.
Those flags will be addressed by a followup patch.
Signed-off-by: Amir Goldstein amir73il@gmail.com Signed-off-by: Miklos Szeredi mszeredi@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org
Sasha,
I do not recommend applying this patch to stable. The value/risk ratio is not worth it IMO.
I don't know of anyone who ever complained about not copying the NOATIME/SYNC fileattrs specifically.
This patch is more of a complimentary patch to the IMMUTABLE/ APPEND fileattr patch, which is not appropriate for stable either.
OTOH, ovl-update-5.15 has this patch that was not included in the AUTOSEL batch, even though it has a Fixes tag, CC stable and very strong hints in the subject: 52d5a0c6bd8a ("ovl: fix BUG_ON() in may_delete() when called from ovl_cleanup()")
I suppose AUTOSEL leaves these sorts of patches to Greg's scripts?
Thanks, Amir.