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SubjectRe: [RFC PATCH 1/4] fs: introduce ->storage_lost() for memory-failure
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On 2020/9/16 上午12:16, Darrick J. Wong wrote:
> On Tue, Sep 15, 2020 at 06:13:08PM +0800, Shiyang Ruan wrote:
>> This function is used to handle errors which may cause data lost in
>> filesystem. Such as memory-failure in fsdax mode.
>>
>> In XFS, it requires "rmapbt" feature in order to query for files or
>> metadata which associated to the error block. Then we could call fs
>> recover functions to try to repair the damaged data.(did not implemented
>> in this patch)
>>
>> After that, the memory-failure also needs to kill processes who are
>> using those files. The struct mf_recover_controller is created to store
>> necessary parameters.
>>
>> Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
>> ---
>> fs/xfs/xfs_super.c | 80 ++++++++++++++++++++++++++++++++++++++++++++++
>> include/linux/fs.h | 1 +
>> include/linux/mm.h | 6 ++++
>> 3 files changed, 87 insertions(+)
>>
>> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
>> index 71ac6c1cdc36..118d9c5d9e1e 100644
>> --- a/fs/xfs/xfs_super.c
>> +++ b/fs/xfs/xfs_super.c
>> @@ -35,6 +35,10 @@
>> #include "xfs_refcount_item.h"
>> #include "xfs_bmap_item.h"
>> #include "xfs_reflink.h"
>> +#include "xfs_alloc.h"
>> +#include "xfs_rmap.h"
>> +#include "xfs_rmap_btree.h"
>> +#include "xfs_bit.h"
>>
>> #include <linux/magic.h>
>> #include <linux/fs_context.h>
>> @@ -1104,6 +1108,81 @@ xfs_fs_free_cached_objects(
>> return xfs_reclaim_inodes_nr(XFS_M(sb), sc->nr_to_scan);
>> }
>>
>> +static int
>> +xfs_storage_lost_helper(
>> + struct xfs_btree_cur *cur,
>> + struct xfs_rmap_irec *rec,
>> + void *priv)
>> +{
>> + struct xfs_inode *ip;
>> + struct mf_recover_controller *mfrc = priv;
>> + int rc = 0;
>> +
>> + if (XFS_RMAP_NON_INODE_OWNER(rec->rm_owner)) {
>> + // TODO check and try to fix metadata
>> + } else {
>> + /*
>> + * Get files that incore, filter out others that are not in use.
>> + */
>> + xfs_iget(cur->bc_mp, cur->bc_tp, rec->rm_owner, XFS_IGET_INCORE,
>> + 0, &ip);
>
> Missing return value check here.

Yes, I ignored it. My fault.

>
>> + if (!ip)
>> + return 0;
>> + if (!VFS_I(ip)->i_mapping)
>> + goto out;
>> +
>> + rc = mfrc->recover_fn(mfrc->pfn, mfrc->flags,
>> + VFS_I(ip)->i_mapping, rec->rm_offset);
>> +
>> + // TODO try to fix data
>> +out:
>> + xfs_irele(ip);
>> + }
>> +
>> + return rc;
>> +}
>> +
>> +static int
>> +xfs_fs_storage_lost(
>> + struct super_block *sb,
>> + loff_t offset,
>
> offset into which device? XFS supports three...
>
> I'm also a little surprised you don't pass in a length.
>
> I guess that means this function will get called repeatedly for every
> byte in the poisoned range?

The memory-failure will triggered on one PFN each time, so its length
could be one PAGE_SIZE. But I think you are right, it's better to tell
filesystem how much range is effected and need to be fixed. I didn't
know but I think there may be some other cases besides memory-failure.
So the length is necessary.

>
>> + void *priv)
>> +{
>> + struct xfs_mount *mp = XFS_M(sb);
>> + struct xfs_trans *tp = NULL;
>> + struct xfs_btree_cur *cur = NULL;
>> + struct xfs_rmap_irec rmap_low, rmap_high;
>> + struct xfs_buf *agf_bp = NULL;
>> + xfs_fsblock_t fsbno = XFS_B_TO_FSB(mp, offset);
>> + xfs_agnumber_t agno = XFS_FSB_TO_AGNO(mp, fsbno);
>> + xfs_agblock_t agbno = XFS_FSB_TO_AGBNO(mp, fsbno);
>> + int error = 0;
>> +
>> + error = xfs_trans_alloc_empty(mp, &tp);
>> + if (error)
>> + return error;
>> +
>> + error = xfs_alloc_read_agf(mp, tp, agno, 0, &agf_bp);
>> + if (error)
>> + return error;
>> +
>> + cur = xfs_rmapbt_init_cursor(mp, tp, agf_bp, agno);
>
> ...and this is definitely the wrong call sequence if the malfunctioning
> device is the realtime device. If a dax rt device dies, you'll be
> shooting down files on the data device, which will cause all sorts of
> problems.

I didn't notice that. Let me think about it.
>
> Question: Should all this poison recovery stuff go into a new file?
> xfs_poison.c? There's already a lot of code in xfs_super.c.

Yes, it's a bit too much. I'll move them into a new file.


--
Thanks,
Ruan Shiyang.
>
> --D
>
>> +
>> + /* Construct a range for rmap query */
>> + memset(&rmap_low, 0, sizeof(rmap_low));
>> + memset(&rmap_high, 0xFF, sizeof(rmap_high));
>> + rmap_low.rm_startblock = rmap_high.rm_startblock = agbno;
>> +
>> + error = xfs_rmap_query_range(cur, &rmap_low, &rmap_high,
>> + xfs_storage_lost_helper, priv);
>> + if (error == -ECANCELED)
>> + error = 0;
>> +
>> + xfs_btree_del_cursor(cur, error);
>> + xfs_trans_brelse(tp, agf_bp);
>> + return error;
>> +}
>> +
>> static const struct super_operations xfs_super_operations = {
>> .alloc_inode = xfs_fs_alloc_inode,
>> .destroy_inode = xfs_fs_destroy_inode,
>> @@ -1117,6 +1196,7 @@ static const struct super_operations xfs_super_operations = {
>> .show_options = xfs_fs_show_options,
>> .nr_cached_objects = xfs_fs_nr_cached_objects,
>> .free_cached_objects = xfs_fs_free_cached_objects,
>> + .storage_lost = xfs_fs_storage_lost,
>> };
>>
>> static int
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index e019ea2f1347..bd90485cfdc9 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -1951,6 +1951,7 @@ struct super_operations {
>> struct shrink_control *);
>> long (*free_cached_objects)(struct super_block *,
>> struct shrink_control *);
>> + int (*storage_lost)(struct super_block *sb, loff_t offset, void *priv);
>> };
>>
>> /*
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index 1983e08f5906..3f0c36e1bf3d 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -3002,6 +3002,12 @@ extern void shake_page(struct page *p, int access);
>> extern atomic_long_t num_poisoned_pages __read_mostly;
>> extern int soft_offline_page(unsigned long pfn, int flags);
>>
>> +struct mf_recover_controller {
>> + int (*recover_fn)(unsigned long pfn, int flags,
>> + struct address_space *mapping, pgoff_t index);
>> + unsigned long pfn;
>> + int flags;
>> +};
>>
>> /*
>> * Error handlers for various types of pages.
>> --
>> 2.28.0
>>
>>
>>
>
>


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