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SubjectRe: [RFC PATCH 1/4] fs: introduce ->storage_lost() for memory-failure
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.

> + 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?

> + 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.

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.

--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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