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SubjectRe: [PATCH 3/3] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind
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在 2022/9/15 2:15, Darrick J. Wong 写道:
> 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.stgit@dwillia2-desk3.amr.corp.intel.com/
>>
>> Signed-off-by: Shiyang Ruan <ruansy.fnst@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 len is U64_MAX, so 'offset + len - 1' will overflow. That can't be
handled correctly by the trimming code below.


--
Thanks,
Ruan.

>
> 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
>>

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