The patch titled
Subject: mm, pmem, xfs: introduce MF_MEM_PRE_REMOVE for unbind
has been added to the -mm mm-unstable branch. Its filename is
mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Subject: mm, pmem, xfs: introduce MF_MEM_PRE_REMOVE for unbind
Date: Mon, 28 Aug 2023 14:57:44 +0800
Now, if we suddenly remove a PMEM device(by calling unbind) which
contains FSDAX while programs are still accessing data in this device,
e.g.:
```
$FSSTRESS_PROG -d $SCRATCH_MNT -n 99999 -p 4 &
# $FSX_PROG -N 1000000 -o 8192 -l 500000 $SCRATCH_MNT/t001 &
echo "pfn1.1" > /sys/bus/nd/drivers/nd_pmem/unbind
```
it could come into an unacceptable state:
1. device has gone but mount point still exists, and umount will fail
with "target is busy"
2. programs will hang and cannot be killed
3. may crash with NULL pointer dereference
To fix this, we introduce a MF_MEM_PRE_REMOVE flag to let it know that we
are going to remove the whole device, and make sure all related processes
could be notified so that they could end up gracefully.
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
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()
-> kill_dax()
-> dax_holder_notify_failure(dax_dev, 0, U64_MAX, MF_MEM_PRE_REMOVE)
-> xfs_dax_notify_failure()
`-> freeze_super() // freeze (kernel call)
`-> do xfs rmap
` -> mf_dax_kill_procs()
` -> collect_procs_fsdax() // all associated processes
` -> unmap_and_kill()
` -> invalidate_inode_pages2_range() // drop file's cache
`-> thaw_super() // thaw (both kernel & user call)
Introduce MF_MEM_PRE_REMOVE to let filesystem know this is a remove
event. Use the exclusive freeze/thaw[2] to lock the filesystem to prevent
new dax mapping from being created. Do not shutdown filesystem directly
if configuration is not supported, or if failure range includes metadata
area. Make sure all files and processes(not only the current progress)
are handled correctly. Also drop the cache of associated files before
pmem is removed.
[1]: https://lore.kernel.org/linux-mm/161604050314.1463742.14151665140035795571.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/
[2]: https://lore.kernel.org/linux-xfs/169116275623.3187159.16862410128731457358.stg-ugh@frogsfrogsfrogs/
Link: https://lkml.kernel.org/r/20230828065744.1446462-1-ruansy.fnst@xxxxxxxxxxx
Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/dax/super.c | 3 -
fs/xfs/xfs_notify_failure.c | 99 +++++++++++++++++++++++++++++++---
include/linux/mm.h | 1
mm/memory-failure.c | 17 ++++-
4 files changed, 109 insertions(+), 11 deletions(-)
--- a/drivers/dax/super.c~mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind
+++ a/drivers/dax/super.c
@@ -326,7 +326,8 @@ 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_PRE_REMOVE);
clear_bit(DAXDEV_ALIVE, &dax_dev->flags);
synchronize_srcu(&dax_srcu);
--- a/fs/xfs/xfs_notify_failure.c~mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind
+++ a/fs/xfs/xfs_notify_failure.c
@@ -22,6 +22,7 @@
#include <linux/mm.h>
#include <linux/dax.h>
+#include <linux/fs.h>
struct xfs_failure_info {
xfs_agblock_t startblock;
@@ -73,10 +74,16 @@ xfs_dax_failure_fn(
struct xfs_mount *mp = cur->bc_mp;
struct xfs_inode *ip;
struct xfs_failure_info *notify = data;
+ struct address_space *mapping;
+ pgoff_t pgoff;
+ unsigned long pgcnt;
int error = 0;
if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) ||
(rec->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK))) {
+ /* Continue the query because this isn't a failure. */
+ if (notify->mf_flags & MF_MEM_PRE_REMOVE)
+ return 0;
notify->want_shutdown = true;
return 0;
}
@@ -92,15 +99,61 @@ xfs_dax_failure_fn(
return 0;
}
- error = mf_dax_kill_procs(VFS_I(ip)->i_mapping,
- xfs_failure_pgoff(mp, rec, notify),
- xfs_failure_pgcnt(mp, rec, notify),
- notify->mf_flags);
+ mapping = VFS_I(ip)->i_mapping;
+ pgoff = xfs_failure_pgoff(mp, rec, notify);
+ pgcnt = xfs_failure_pgcnt(mp, rec, notify);
+
+ /* Continue the rmap query if the inode isn't a dax file. */
+ if (dax_mapping(mapping))
+ error = mf_dax_kill_procs(mapping, pgoff, pgcnt,
+ notify->mf_flags);
+
+ /* Invalidate the cache in dax pages. */
+ if (notify->mf_flags & MF_MEM_PRE_REMOVE)
+ invalidate_inode_pages2_range(mapping, pgoff,
+ pgoff + pgcnt - 1);
+
xfs_irele(ip);
return error;
}
static int
+xfs_dax_notify_failure_freeze(
+ struct xfs_mount *mp)
+{
+ struct super_block *sb = mp->m_super;
+ int error;
+
+ error = freeze_super(sb, FREEZE_HOLDER_KERNEL);
+ if (error)
+ xfs_emerg(mp, "already frozen by kernel, err=%d", error);
+
+ return error;
+}
+
+static void
+xfs_dax_notify_failure_thaw(
+ struct xfs_mount *mp,
+ bool kernel_frozen)
+{
+ struct super_block *sb = mp->m_super;
+ int error;
+
+ if (kernel_frozen) {
+ error = thaw_super(sb, FREEZE_HOLDER_KERNEL);
+ if (error)
+ xfs_emerg(mp, "still frozen after notify failure, err=%d",
+ error);
+ }
+
+ /*
+ * Also thaw userspace call anyway because the device is about to be
+ * removed immediately.
+ */
+ thaw_super(sb, FREEZE_HOLDER_USERSPACE);
+}
+
+static int
xfs_dax_notify_ddev_failure(
struct xfs_mount *mp,
xfs_daddr_t daddr,
@@ -112,15 +165,29 @@ xfs_dax_notify_ddev_failure(
struct xfs_btree_cur *cur = NULL;
struct xfs_buf *agf_bp = NULL;
int error = 0;
+ bool kernel_frozen = false;
xfs_fsblock_t fsbno = XFS_DADDR_TO_FSB(mp, daddr);
xfs_agnumber_t agno = XFS_FSB_TO_AGNO(mp, fsbno);
xfs_fsblock_t end_fsbno = XFS_DADDR_TO_FSB(mp,
daddr + bblen - 1);
xfs_agnumber_t end_agno = XFS_FSB_TO_AGNO(mp, end_fsbno);
+ if (mf_flags & MF_MEM_PRE_REMOVE) {
+ xfs_info(mp, "Device is about to be removed!");
+ /*
+ * Freeze fs to prevent new mappings from being created.
+ * - Keep going on if others already hold the kernel forzen.
+ * - Keep going on if other errors too because this device is
+ * starting to fail.
+ * - If kernel frozen state is hold successfully here, thaw it
+ * here as well at the end.
+ */
+ kernel_frozen = xfs_dax_notify_failure_freeze(mp) == 0;
+ }
+
error = xfs_trans_alloc_empty(mp, &tp);
if (error)
- return error;
+ goto out;
for (; agno <= end_agno; agno++) {
struct xfs_rmap_irec ri_low = { };
@@ -165,11 +232,23 @@ xfs_dax_notify_ddev_failure(
}
xfs_trans_cancel(tp);
+
+ /*
+ * Determine how to shutdown the filesystem according to the
+ * error code and flags.
+ */
if (error || notify.want_shutdown) {
xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_ONDISK);
if (!error)
error = -EFSCORRUPTED;
- }
+ } else if (mf_flags & MF_MEM_PRE_REMOVE)
+ xfs_force_shutdown(mp, SHUTDOWN_FORCE_UMOUNT);
+
+out:
+ /* Thaw the fs if it is frozen before. */
+ if (mf_flags & MF_MEM_PRE_REMOVE)
+ xfs_dax_notify_failure_thaw(mp, kernel_frozen);
+
return error;
}
@@ -197,6 +276,8 @@ 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_PRE_REMOVE)
+ return 0;
xfs_err(mp, "ondisk log corrupt, shutting down fs!");
xfs_force_shutdown(mp, SHUTDOWN_CORRUPT_ONDISK);
return -EFSCORRUPTED;
@@ -210,6 +291,12 @@ xfs_dax_notify_failure(
ddev_start = mp->m_ddev_targp->bt_dax_part_off;
ddev_end = ddev_start + bdev_nr_bytes(mp->m_ddev_targp->bt_bdev) - 1;
+ /* Notify failure on the whole device. */
+ if (offset == 0 && len == U64_MAX) {
+ offset = ddev_start;
+ len = bdev_nr_bytes(mp->m_ddev_targp->bt_bdev);
+ }
+
/* Ignore the range out of filesystem area */
if (offset + len - 1 < ddev_start)
return -ENXIO;
--- a/include/linux/mm.h~mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind
+++ a/include/linux/mm.h
@@ -3782,6 +3782,7 @@ enum mf_flags {
MF_UNPOISON = 1 << 4,
MF_SW_SIMULATED = 1 << 5,
MF_NO_RETRY = 1 << 6,
+ MF_MEM_PRE_REMOVE = 1 << 7,
};
int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
unsigned long count, int mf_flags);
--- a/mm/memory-failure.c~mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind
+++ a/mm/memory-failure.c
@@ -679,7 +679,7 @@ static void add_to_kill_fsdax(struct tas
*/
static void collect_procs_fsdax(struct page *page,
struct address_space *mapping, pgoff_t pgoff,
- struct list_head *to_kill)
+ struct list_head *to_kill, bool pre_remove)
{
struct vm_area_struct *vma;
struct task_struct *tsk;
@@ -687,8 +687,15 @@ static void collect_procs_fsdax(struct p
i_mmap_lock_read(mapping);
read_lock(&tasklist_lock);
for_each_process(tsk) {
- struct task_struct *t = task_early_kill(tsk, true);
+ struct task_struct *t = tsk;
+ /*
+ * Search for all tasks while MF_MEM_PRE_REMOVE is set, because
+ * the current may not be the one accessing the fsdax page.
+ * Otherwise, search for the current task.
+ */
+ if (!pre_remove)
+ t = task_early_kill(tsk, true);
if (!t)
continue;
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
@@ -1792,6 +1799,7 @@ int mf_dax_kill_procs(struct address_spa
dax_entry_t cookie;
struct page *page;
size_t end = index + count;
+ bool pre_remove = mf_flags & MF_MEM_PRE_REMOVE;
mf_flags |= MF_ACTION_REQUIRED | MF_MUST_KILL;
@@ -1803,9 +1811,10 @@ int mf_dax_kill_procs(struct address_spa
if (!page)
goto unlock;
- SetPageHWPoison(page);
+ if (!pre_remove)
+ SetPageHWPoison(page);
- collect_procs_fsdax(page, mapping, index, &to_kill);
+ collect_procs_fsdax(page, mapping, index, &to_kill, pre_remove);
unmap_and_kill(&to_kill, page_to_pfn(page), mapping,
index, mf_flags);
unlock:
_
Patches currently in -mm which might be from ruansy.fnst@xxxxxxxxxxx are
mm-pmem-xfs-introduce-mf_mem_pre_remove-for-unbind.patch
