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    SubjectRe: [PATCH v3 3/6] mm: shrinkers: provide shrinkers with names
    On Mon, May 09, 2022 at 11:38:17AM -0700, Roman Gushchin wrote:
    > Currently shrinkers are anonymous objects. For debugging purposes they
    > can be identified by count/scan function names, but it's not always
    > useful: e.g. for superblock's shrinkers it's nice to have at least
    > an idea of to which superblock the shrinker belongs.
    >
    > This commit adds names to shrinkers. register_shrinker() and
    > prealloc_shrinker() functions are extended to take a format and
    > arguments to master a name.
    >
    > In some cases it's not possible to determine a good name at the time
    > when a shrinker is allocated. For such cases shrinker_debugfs_rename()
    > is provided.
    >
    > After this change the shrinker debugfs directory looks like:
    > $ cd /sys/kernel/debug/shrinker/
    > $ ls
    > dqcache-16 sb-hugetlbfs-17 sb-rootfs-2 sb-tmpfs-50
    > kfree_rcu-0 sb-hugetlbfs-33 sb-securityfs-6 sb-tracefs-13
    > sb-aio-20 sb-iomem-12 sb-selinuxfs-22 sb-xfs:vda1-36
    > sb-anon_inodefs-15 sb-mqueue-21 sb-sockfs-8 sb-zsmalloc-19
    > sb-bdev-3 sb-nsfs-4 sb-sysfs-26 shadow-18
    > sb-bpf-32 sb-pipefs-14 sb-tmpfs-1 thp_deferred_split-10
    > sb-btrfs:vda2-24 sb-proc-25 sb-tmpfs-27 thp_zero-9
    > sb-cgroup2-30 sb-proc-39 sb-tmpfs-29 xfs_buf-37
    > sb-configfs-23 sb-proc-41 sb-tmpfs-35 xfs_inodegc-38
    ^^^^^^^^^^^^^^

    These XFS shrinkers are also per-block device like the superblock.
    They need to read like "sb-xfs:vda1-36". and even though it is not
    in this list, the xfs dquot shrinker will need this as well.


    > sb-dax-11 sb-proc-45 sb-tmpfs-40 zspool-34
    > sb-debugfs-7 sb-proc-46 sb-tmpfs-42
    > sb-devpts-28 sb-proc-47 sb-tmpfs-43
    > sb-devtmpfs-5 sb-pstore-31 sb-tmpfs-44

    The proc and tmpfs shrinkers have the same problem - what instance
    do they actually refer to?

    > diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
    > index e1afb9e503e1..5645e92df0c9 100644
    > --- a/fs/xfs/xfs_buf.c
    > +++ b/fs/xfs/xfs_buf.c
    > @@ -1986,7 +1986,7 @@ xfs_alloc_buftarg(
    > btp->bt_shrinker.scan_objects = xfs_buftarg_shrink_scan;
    > btp->bt_shrinker.seeks = DEFAULT_SEEKS;
    > btp->bt_shrinker.flags = SHRINKER_NUMA_AWARE;
    > - if (register_shrinker(&btp->bt_shrinker))
    > + if (register_shrinker(&btp->bt_shrinker, "xfs_buf"))
    > goto error_pcpu;
    > return btp;
    >
    > diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
    > index bffd6eb0b298..d0c4e74ff763 100644
    > --- a/fs/xfs/xfs_icache.c
    > +++ b/fs/xfs/xfs_icache.c
    > @@ -2198,5 +2198,5 @@ xfs_inodegc_register_shrinker(
    > shrink->flags = SHRINKER_NONSLAB;
    > shrink->batch = XFS_INODEGC_SHRINKER_BATCH;
    >
    > - return register_shrinker(shrink);
    > + return register_shrinker(shrink, "xfs_inodegc");
    > }
    > diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
    > index f165d1a3de1d..93ded9e81f49 100644
    > --- a/fs/xfs/xfs_qm.c
    > +++ b/fs/xfs/xfs_qm.c
    > @@ -686,7 +686,7 @@ xfs_qm_init_quotainfo(
    > qinf->qi_shrinker.seeks = DEFAULT_SEEKS;
    > qinf->qi_shrinker.flags = SHRINKER_NUMA_AWARE;
    >
    > - error = register_shrinker(&qinf->qi_shrinker);
    > + error = register_shrinker(&qinf->qi_shrinker, "xfs_qm");
    > if (error)
    > goto out_free_inos;

    Yeah, these all have a xfs_mount passed to them, so the superblock is
    easily accessible here (mp->m_super)....

    Cheers,

    Dave.
    --
    Dave Chinner
    dchinner@redhat.com

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