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/168688010689.860947.1788875898367401950.stgit@frogsfrogsfrogs/
Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
---
drivers/dax/super.c | 3 +-
fs/xfs/xfs_notify_failure.c | 86 ++++++++++++++++++++++++++++++++++---
include/linux/mm.h | 1 +
mm/memory-failure.c | 17 ++++++--
4 files changed, 96 insertions(+), 11 deletions(-)
diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index c4c4728a36e4..2e1a35e82fce 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -323,7 +323,8 @@ 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);
diff --git a/fs/xfs/xfs_notify_failure.c b/fs/xfs/xfs_notify_failure.c
index 4a9bbd3fe120..f6ec56b76db6 100644
--- a/fs/xfs/xfs_notify_failure.c
+++ b/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;
}
@@ -92,14 +99,55 @@ 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 void
+xfs_dax_notify_failure_freeze(
+ struct xfs_mount *mp)
+{
+ struct super_block *sb = mp->m_super;
+
+ /* Wait until no one is holding the FREEZE_HOLDER_KERNEL. */
+ while (freeze_super(sb, FREEZE_HOLDER_KERNEL) != 0) {
+ // Shall we just wait, or print warning then return -EBUSY?
+ delay(HZ / 10);
+ }
+}
+
+static void
+xfs_dax_notify_failure_thaw(
+ struct xfs_mount *mp)
+{
+ struct super_block *sb = mp->m_super;
+ int error;
+
+ 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,
@@ -120,7 +168,7 @@ xfs_dax_notify_ddev_failure(
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 +213,23 @@ 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 freezed before. */
+ if (mf_flags & MF_MEM_PRE_REMOVE)
+ xfs_dax_notify_failure_thaw(mp);
+
return error;
}
@@ -197,6 +257,8 @@ 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 +272,12 @@ 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;
@@ -226,6 +294,12 @@ xfs_dax_notify_failure(
if (offset + len - 1 > ddev_end)
len = ddev_end - offset + 1;
+ 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. */
+ xfs_dax_notify_failure_freeze(mp);
+ }
+
return xfs_dax_notify_ddev_failure(mp, BTOBB(offset), BTOBB(len),
mf_flags);
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 27ce77080c79..a80c255b88d2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3576,6 +3576,7 @@ 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);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 5b663eca1f29..483b75f2fcfb 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -688,7 +688,7 @@ static void add_to_kill_fsdax(struct task_struct *tsk, struct page *p,
*/
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;
@@ -696,8 +696,15 @@ static void collect_procs_fsdax(struct page *page,
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, 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) {
@@ -1793,6 +1800,7 @@ int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
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;
@@ -1804,9 +1812,10 @@ int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
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:
--
2.40.1
