On Sun, Dec 13, 2020 at 08:27:13AM -0500, Jeff Layton wrote:
> Peek at the upper layer's errseq_t at mount time for volatile mounts,
> and record it in the per-sb info. In sync_fs, check for an error since
> the recorded point and set it in the overlayfs superblock if there was
> one.
>
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
While we are solving problem for non-volatile overlay mount, I also
started thinking, what about non-volatile overlay syncfs() writeback errors.
Looks like these will not be reported to user space at all as of now
(because we never update overlay_sb->s_wb_err ever).
A patch like this might fix it. (compile tested only).
overlayfs: Report syncfs() errors to user space
Currently, syncfs(), calls filesystem ->sync_fs() method but ignores the
return code. But certain writeback errors can still be reported on
syncfs() by checking errors on super block.
ret2 = errseq_check_and_advance(&sb->s_wb_err, &f.file->f_sb_err);
For the case of overlayfs, we never set overlayfs super block s_wb_err. That
means sync() will never report writeback errors on overlayfs uppon syncfs().
Fix this by updating overlay sb->sb_wb_err upon ->sync_fs() call. And that
should mean that user space syncfs() call should see writeback errors.
ovl_fsync() does not need anything special because if there are writeback
errors underlying filesystem will report it through vfs_fsync_range() return
code and user space will see it.
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
fs/overlayfs/ovl_entry.h | 1 +
fs/overlayfs/super.c | 14 +++++++++++---
2 files changed, 12 insertions(+), 3 deletions(-)
Index: redhat-linux/fs/overlayfs/super.c
===================================================================
--- redhat-linux.orig/fs/overlayfs/super.c 2020-12-14 15:33:43.934400880 -0500
+++ redhat-linux/fs/overlayfs/super.c 2020-12-14 16:15:07.127400880 -0500
@@ -259,7 +259,7 @@ static int ovl_sync_fs(struct super_bloc
{
struct ovl_fs *ofs = sb->s_fs_info;
struct super_block *upper_sb;
- int ret;
+ int ret, ret2;
if (!ovl_upper_mnt(ofs))
return 0;
@@ -283,7 +283,14 @@ static int ovl_sync_fs(struct super_bloc
ret = sync_filesystem(upper_sb);
up_read(&upper_sb->s_umount);
- return ret;
+ if (errseq_check(&upper_sb->s_wb_err, sb->s_wb_err)) {
+ /* Upper sb has errors since last time */
+ spin_lock(&ofs->errseq_lock);
+ ret2 = errseq_check_and_advance(&upper_sb->s_wb_err,
+ &sb->s_wb_err);
+ spin_unlock(&ofs->errseq_lock);
+ }
+ return ret ? ret : ret2;
}
/**
@@ -1873,6 +1880,7 @@ static int ovl_fill_super(struct super_b
if (!cred)
goto out_err;
+ spin_lock_init(&ofs->errseq_lock);
/* Is there a reason anyone would want not to share whiteouts? */
ofs->share_whiteout = true;
@@ -1945,7 +1953,7 @@ static int ovl_fill_super(struct super_b
sb->s_stack_depth = ovl_upper_mnt(ofs)->mnt_sb->s_stack_depth;
sb->s_time_gran = ovl_upper_mnt(ofs)->mnt_sb->s_time_gran;
-
+ sb->s_wb_err = errseq_sample(&ovl_upper_mnt(ofs)->mnt_sb->s_wb_err);
}
oe = ovl_get_lowerstack(sb, splitlower, numlower, ofs, layers);
err = PTR_ERR(oe);
Index: redhat-linux/fs/overlayfs/ovl_entry.h
===================================================================
--- redhat-linux.orig/fs/overlayfs/ovl_entry.h 2020-12-14 15:33:43.934400880 -0500
+++ redhat-linux/fs/overlayfs/ovl_entry.h 2020-12-14 15:34:13.509400880 -0500
@@ -79,6 +79,7 @@ struct ovl_fs {
atomic_long_t last_ino;
/* Whiteout dentry cache */
struct dentry *whiteout;
+ spinlock_t errseq_lock;
};
static inline struct vfsmount *ovl_upper_mnt(struct ovl_fs *ofs)
