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SubjectRe: [RFC PATCH 2/4] pagemap: introduce ->memory_failure()
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On 2020/9/16 上午12:31, Darrick J. Wong wrote:
> On Tue, Sep 15, 2020 at 06:13:09PM +0800, Shiyang Ruan wrote:
>> When memory-failure occurs, we call this function which is implemented
>> by each devices. For fsdax, pmem device implements it. Pmem device
>> will find out the block device where the error page located in, gets the
>> filesystem on this block device, and finally call ->storage_lost() to
>> handle the error in filesystem layer.
>>
>> Normally, a pmem device may contain one or more partitions, each
>> partition contains a block device, each block device contains a
>> filesystem. So we are able to find out the filesystem by one offset on
>> this pmem device. However, in other cases, such as mapped device, I
>> didn't find a way to obtain the filesystem laying on it. It is a
>> problem need to be fixed.
>>
>> Signed-off-by: Shiyang Ruan <ruansy.fnst@cn.fujitsu.com>
>> ---
>> block/genhd.c | 12 ++++++++++++
>> drivers/nvdimm/pmem.c | 31 +++++++++++++++++++++++++++++++
>> include/linux/genhd.h | 2 ++
>> include/linux/memremap.h | 3 +++
>> 4 files changed, 48 insertions(+)
>>
>> diff --git a/block/genhd.c b/block/genhd.c
>> index 99c64641c314..e7442b60683e 100644
>> --- a/block/genhd.c
>> +++ b/block/genhd.c
>> @@ -1063,6 +1063,18 @@ struct block_device *bdget_disk(struct gendisk *disk, int partno)
>> }
>> EXPORT_SYMBOL(bdget_disk);
>>
>> +struct block_device *bdget_disk_sector(struct gendisk *disk, sector_t sector)
>> +{
>> + struct block_device *bdev = NULL;
>> + struct hd_struct *part = disk_map_sector_rcu(disk, sector);
>> +
>> + if (part)
>> + bdev = bdget(part_devt(part));
>> +
>> + return bdev;
>> +}
>> +EXPORT_SYMBOL(bdget_disk_sector);
>> +
>> /*
>> * print a full list of all partitions - intended for places where the root
>> * filesystem can't be mounted and thus to give the victim some idea of what
>> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
>> index fab29b514372..3ed96486c883 100644
>> --- a/drivers/nvdimm/pmem.c
>> +++ b/drivers/nvdimm/pmem.c
>> @@ -364,9 +364,40 @@ static void pmem_release_disk(void *__pmem)
>> put_disk(pmem->disk);
>> }
>>
>> +static int pmem_pagemap_memory_failure(struct dev_pagemap *pgmap,
>> + struct mf_recover_controller *mfrc)
>> +{
>> + struct pmem_device *pdev;
>> + struct block_device *bdev;
>> + sector_t disk_sector;
>> + loff_t bdev_offset;
>> +
>> + pdev = container_of(pgmap, struct pmem_device, pgmap);
>> + if (!pdev->disk)
>> + return -ENXIO;
>> +
>> + disk_sector = (PFN_PHYS(mfrc->pfn) - pdev->phys_addr) >> SECTOR_SHIFT;
>
> Ah, I see, looking at the current x86 MCE code, the MCE handler gets a
> physical address, which is then rounded down to a PFN, which is then
> blown back up into a byte address(?) and then rounded down to sectors.
> That is then blown back up into a byte address and passed on to XFS,
> which rounds it down to fs blocksize.
>
> /me wishes that wasn't so convoluted, but reforming the whole mm poison
> system to have smaller blast radii isn't the purpose of this patch. :)
>
>> + bdev = bdget_disk_sector(pdev->disk, disk_sector);
>> + if (!bdev)
>> + return -ENXIO;
>> +
>> + // TODO what if block device contains a mapped device
>
> Find its dev_pagemap_ops and invoke its memory_failure function? ;)

Thanks for pointing out. I'll think about it in this way.
>
>> + if (!bdev->bd_super)
>> + goto out;
>> +
>> + bdev_offset = ((disk_sector - get_start_sect(bdev)) << SECTOR_SHIFT) -
>> + pdev->data_offset;
>> + bdev->bd_super->s_op->storage_lost(bdev->bd_super, bdev_offset, mfrc);
>
> ->storage_lost is required for all filesystems?

I think it is required for filesystems that support fsdax, since the
owner tracking is moved here. But anyway, there should have a non-NULL
judgment.


--
Thanks,
Ruan Shiyang.
>
> --D
>
>> +
>> +out:
>> + bdput(bdev);
>> + return 0;
>> +}
>> +
>> static const struct dev_pagemap_ops fsdax_pagemap_ops = {
>> .kill = pmem_pagemap_kill,
>> .cleanup = pmem_pagemap_cleanup,
>> + .memory_failure = pmem_pagemap_memory_failure,
>> };
>>
>> static int pmem_attach_disk(struct device *dev,
>> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
>> index 4ab853461dff..16e9e13e0841 100644
>> --- a/include/linux/genhd.h
>> +++ b/include/linux/genhd.h
>> @@ -303,6 +303,8 @@ static inline void add_disk_no_queue_reg(struct gendisk *disk)
>> extern void del_gendisk(struct gendisk *gp);
>> extern struct gendisk *get_gendisk(dev_t dev, int *partno);
>> extern struct block_device *bdget_disk(struct gendisk *disk, int partno);
>> +extern struct block_device *bdget_disk_sector(struct gendisk *disk,
>> + sector_t sector);
>>
>> extern void set_device_ro(struct block_device *bdev, int flag);
>> extern void set_disk_ro(struct gendisk *disk, int flag);
>> diff --git a/include/linux/memremap.h b/include/linux/memremap.h
>> index 5f5b2df06e61..efebefa70d00 100644
>> --- a/include/linux/memremap.h
>> +++ b/include/linux/memremap.h
>> @@ -6,6 +6,7 @@
>>
>> struct resource;
>> struct device;
>> +struct mf_recover_controller;
>>
>> /**
>> * struct vmem_altmap - pre-allocated storage for vmemmap_populate
>> @@ -87,6 +88,8 @@ struct dev_pagemap_ops {
>> * the page back to a CPU accessible page.
>> */
>> vm_fault_t (*migrate_to_ram)(struct vm_fault *vmf);
>> + int (*memory_failure)(struct dev_pagemap *pgmap,
>> + struct mf_recover_controller *mfrc);
>> };
>>
>> #define PGMAP_ALTMAP_VALID (1 << 0)
>> --
>> 2.28.0
>>
>>
>>
>
>


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