Volatile remounts validate the following at the moment:
* Has the module been reloaded / the system rebooted
* Has the workdir been remounted
This adds a new check for errors detected via the superblock's
errseq_t. At mount time, the errseq_t is snapshotted to disk,
and upon remount it's re-verified. This allows for kernel-level
detection of errors without forcing userspace to perform a
sync and allows for the hidden detection of writeback errors.
Signed-off-by: Sargun Dhillon <sargun@xxxxxxxxx>
---
fs/overlayfs/overlayfs.h | 1 +
fs/overlayfs/readdir.c | 6 ++++++
fs/overlayfs/super.c | 1 +
3 files changed, 8 insertions(+)
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index de694ee99d7c..e8a711953b64 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -85,6 +85,7 @@ struct ovl_volatile_info {
*/
uuid_t ovl_boot_id; /* Must stay first member */
u64 s_instance_id;
+ errseq_t errseq; /* Implemented as a u32 */
} __packed;
/*
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 4e3e2bc3ea43..2bb0641ecbbd 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -1109,6 +1109,12 @@ static int ovl_verify_volatile_info(struct ovl_fs *ofs,
return -EINVAL;
}
+ err = errseq_check(&volatiledir->d_sb->s_wb_err, info.errseq);
+ if (err) {
+ pr_debug("Workdir filesystem reports errors: %d\n", err);
+ return -EINVAL;
+ }
+
return 1;
}
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 9a1b07907662..49dee41ec125 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -1248,6 +1248,7 @@ static int ovl_set_volatile_info(struct ovl_fs *ofs, struct dentry *volatiledir)
int err;
struct ovl_volatile_info info = {
.s_instance_id = volatiledir->d_sb->s_instance_id,
+ .errseq = errseq_sample(&volatiledir->d_sb->s_wb_err),
};
uuid_copy(&info.ovl_boot_id, &ovl_boot_id);
--
2.25.1
