[RFC PATCH v2] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind

Shiyang Ruan
2022-05-20T05:37:40Z

This patch is inspired by Dan's "mm, dax, pmem: Introduce
dev_pagemap_failure()"[1]. With the help of dax_holder and
->notify_failure() mechanism, the pmem driver is able to ask filesystem
(or mapped device) on it to unmap all files in use and notify processes
who are using those files.

Call trace:
trigger unbind
-> unbind_store()
-> ... (skip)
-> devres_release_all() # was pmem driver ->remove() in v1
-> kill_dax()
-> dax_holder_notify_failure(dax_dev, 0, U64_MAX, MF_MEM_REMOVE)
-> xfs_dax_notify_failure()

Introduce MF_MEM_REMOVE to let filesystem know this is a remove event.
So do not shutdown filesystem directly if something not supported, or if
failure range includes metadata area. Make sure all files and processes
are handled correctly.

[1]: https://lore.kernel.org/linux-mm/161604050314.1463742.14151665140035795571.stgit@dwillia2-desk3.amr.corp.intel.com/
[2]: https://lore.kernel.org/linux-xfs/20220508143620.1775214-1-ruansy.fnst@fujitsu.com/

Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>

==
Changes since v1:
1. Drop the needless change of moving {kill,put}_dax()
2. Rebased on '[PATCHSETS] v14 fsdax-rmap + v11 fsdax-reflink'[2]

---
drivers/dax/super.c | 2 +-
fs/xfs/xfs_notify_failure.c | 6 +++++-
include/linux/mm.h | 1 +
3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index 5ddb159c4653..44ca3b488e2a 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -313,7 +313,7 @@ void kill_dax(struct dax_device *dax_dev)
return;

if (dax_dev->holder_data != NULL)
- dax_holder_notify_failure(dax_dev, 0, U64_MAX, 0);
+ dax_holder_notify_failure(dax_dev, 0, U64_MAX, MF_MEM_REMOVE);

clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
synchronize_srcu(&dax_srcu);
diff --git a/fs/xfs/xfs_notify_failure.c b/fs/xfs/xfs_notify_failure.c
index aa8dc27c599c..91d3f05d4241 100644
--- a/fs/xfs/xfs_notify_failure.c
+++ b/fs/xfs/xfs_notify_failure.c
@@ -73,7 +73,9 @@ xfs_dax_failure_fn(
struct failure_info *notify = data;
int error = 0;

- if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) ||
+ /* Do not shutdown so early when device is to be removed */
+ if (!(notify->mf_flags & MF_MEM_REMOVE) ||
+ XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) ||
(rec->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK))) {
xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_ONDISK);
return -EFSCORRUPTED;
@@ -182,6 +184,8 @@ xfs_dax_notify_failure(

if (mp->m_logdev_targp && mp->m_logdev_targp->bt_daxdev == dax_dev &&
mp->m_logdev_targp != mp->m_ddev_targp) {
+ if (mf_flags & MF_MEM_REMOVE)
+ return -EOPNOTSUPP;
xfs_err(mp, "ondisk log corrupt, shutting down fs!");
xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_ONDISK);
return -EFSCORRUPTED;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index e2c0f69f0660..ebcb5a7f3295 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3226,6 +3226,7 @@ enum mf_flags {
MF_MUST_KILL = 1 << 2,
MF_SOFT_OFFLINE = 1 << 3,
MF_UNPOISON = 1 << 4,
+ MF_MEM_REMOVE = 1 << 5,
};
int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
unsigned long count, int mf_flags);
--
2.35.1