Re: [PATCH v12 2/2] mm, pmem, xfs: Introduce MF_MEM_REMOVE for unbind

[Shiyang Ruan <ruansy.fnst@fujitsu.com>]

在 2023/7/14 22:18, Darrick J. Wong 写道:
> On Fri, Jul 14, 2023 at 05:07:58PM +0800, Shiyang Ruan wrote:
>> Hi Darrick,
>>
>> Thanks for applying the 1st patch.
>>
>> Now, since this patch is based on the new freeze_super()/thaw_super()
>> api[1], I'd like to ask what's the plan for this api?  It seems to have
>> missed the v6.5-rc1.
>>
>> [1] https://lore.kernel.org/linux-xfs/168688010689.860947.1788875898367401950.stgit@frogsfrogsfrogs/
> 
> 6.6.  I intend to push the XFS UBSAN fixes to the list today for review.
> Early next week I'll resend the 6.5 rebase of the kernelfreeze series
> and push it to vfs-for-next.  Some time after that will come large folio
> writes.

Got it.  Thanks for your information!


--
Ruan.

> 
> --D
> 
>>
>> --
>> Thanks,
>> Ruan.
>>
>>
>> 在 2023/6/29 16:16, Shiyang Ruan 写道:
>>> 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@dwillia2-desk3.amr.corp.intel.com/
>>> [2]: https://lore.kernel.org/linux-xfs/168688010689.860947.1788875898367401950.stgit@frogsfrogsfrogs/
>>>
>>> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
>>> ---
>>>    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: