On Fri, Sep 02, 2022 at 10:36:01AM +0000, Shiyang Ruan wrote:
> 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_PRE_REMOVE)
> -> xfs_dax_notify_failure()
>
> Introduce MF_MEM_PRE_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.st...@dwillia2-desk3.amr.corp.intel.com/
>
> Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com>
> ---
> drivers/dax/super.c | 3 ++-
> fs/xfs/xfs_notify_failure.c | 23 +++++++++++++++++++++++
> include/linux/mm.h | 1 +
> 3 files changed, 26 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dax/super.c b/drivers/dax/super.c
> index 9b5e2a5eb0ae..cf9a64563fbe 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 3830f908e215..5e04ba7fa403 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;
> @@ -77,6 +78,9 @@ xfs_dax_failure_fn(
>
> if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner) ||
> (rec->rm_flags & (XFS_RMAP_ATTR_FORK | XFS_RMAP_BMBT_BLOCK))) {
> + /* The device is about to be removed. Not a really failure. */
> + if (notify->mf_flags & MF_MEM_PRE_REMOVE)
> + return 0;
> notify->want_shutdown = true;
> return 0;
> }
> @@ -182,12 +186,23 @@ xfs_dax_notify_failure(
> struct xfs_mount *mp = dax_holder(dax_dev);
> u64 ddev_start;
> u64 ddev_end;
> + int error;
>
> if (!(mp->m_super->s_flags & SB_BORN)) {
> xfs_warn(mp, "filesystem is not ready for notify_failure()!");
> return -EIO;
> }
>
> + if (mf_flags & MF_MEM_PRE_REMOVE) {
> + xfs_info(mp, "device is about to be removed!");
> + down_write(&mp->m_super->s_umount);
> + error = sync_filesystem(mp->m_super);
> + drop_pagecache_sb(mp->m_super, NULL);
> + up_write(&mp->m_super->s_umount);
> + if (error)
> + return error;
> + }
> +
> if (mp->m_rtdev_targp && mp->m_rtdev_targp->bt_daxdev == dax_dev) {
> xfs_debug(mp,
> "notify_failure() not supported on realtime device!");
> @@ -196,6 +211,8 @@ 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;
> @@ -209,6 +226,12 @@ 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);
> + }
I wonder, won't the trimming code below take care of this?
The rest of the patch looks ok to me.
--D
> +
> /* Ignore the range out of filesystem area */
> if (offset + len - 1 < ddev_start)
> return -ENXIO;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 21f8b27bd9fd..9122a1c57dd2 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3183,6 +3183,7 @@ 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);
> --
> 2.37.2
>
