as requested and argued in:
https://lore.proxmox.com/pve-devel/5f3e46ed-bf99-45e2-b497-fc81dc50d...@proxmox.com/
Signed-off-by: Stoiko Ivanov <s.iva...@proxmox.com>
---
If accepted we'd try to include the backport upstream for 2.2.9
...kport-enforce-arc_dnode_limit-to-2.2.patch | 207 ++++++++++++++++++
debian/patches/series | 1 +
2 files changed, 208 insertions(+)
create mode 100644
debian/patches/0012-backport-enforce-arc_dnode_limit-to-2.2.patch
diff --git a/debian/patches/0012-backport-enforce-arc_dnode_limit-to-2.2.patch
b/debian/patches/0012-backport-enforce-arc_dnode_limit-to-2.2.patch
new file mode 100644
index 000000000..26c0dface
--- /dev/null
+++ b/debian/patches/0012-backport-enforce-arc_dnode_limit-to-2.2.patch
@@ -0,0 +1,207 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Stoiko Ivanov <s.iva...@proxmox.com>
+Date: Mon, 28 Jul 2025 15:16:46 +0200
+Subject: [PATCH] backport enforce arc_dnode_limit to 2.2
+
+This patch is a backport of a7a144e65 ("enforce arc_dnode_limit")
+for the 2.2 branch.
+
+back-ported from commit a7a144e655850b4160943e4ba315eb9a5dc2b2fe
+working around changes from:
+55427add3 ("Several improvements to ARC shrinking (#16197)")
+5b9f3b766 ("Soften pruning threshold on not evictable metadata")
+which are present in 2.2.3, but not in 2.2.8
+
+Signed-off-by: Stoiko Ivanov <s.iva...@proxmox.com>
+---
+ include/sys/arc_impl.h | 2 +-
+ module/os/linux/zfs/zfs_vfsops.c | 65 ++++++++++++++++++++++++++++++++
+ module/zfs/arc.c | 27 ++++++++-----
+ 3 files changed, 83 insertions(+), 11 deletions(-)
+
+diff --git a/include/sys/arc_impl.h b/include/sys/arc_impl.h
+index
defebe3b2fbbdc8b1c901108f19bde8f12ea2175..36cd83e83358e123980909a903854d573531d4b6
100644
+--- a/include/sys/arc_impl.h
++++ b/include/sys/arc_impl.h
+@@ -952,7 +952,7 @@ typedef struct arc_sums {
+ wmsum_t arcstat_data_size;
+ wmsum_t arcstat_metadata_size;
+ wmsum_t arcstat_dbuf_size;
+- wmsum_t arcstat_dnode_size;
++ aggsum_t arcstat_dnode_size;
+ wmsum_t arcstat_bonus_size;
+ wmsum_t arcstat_l2_hits;
+ wmsum_t arcstat_l2_misses;
+diff --git a/module/os/linux/zfs/zfs_vfsops.c
b/module/os/linux/zfs/zfs_vfsops.c
+index
1f72cce07dd1830e2f5fdff50ef298e05be3013d..da0cda03985e93acfa111efb7d6e9d6637f729cf
100644
+--- a/module/os/linux/zfs/zfs_vfsops.c
++++ b/module/os/linux/zfs/zfs_vfsops.c
+@@ -1179,6 +1179,63 @@ zfs_root(zfsvfs_t *zfsvfs, struct inode **ipp)
+ return (error);
+ }
+
++/*
++ * Dentry and inode caches referenced by a task in non-root memcg are
++ * not going to be scanned by the kernel-provided shrinker. So, if
++ * kernel prunes nothing, fall back to this manual walk to free dnodes.
++ * To avoid scanning the same znodes multiple times they are always rotated
++ * to the end of the z_all_znodes list. New znodes are inserted at the
++ * end of the list so we're always scanning the oldest znodes first.
++ */
++static int
++zfs_prune_aliases(zfsvfs_t *zfsvfs, unsigned long nr_to_scan)
++{
++ znode_t **zp_array, *zp;
++ int max_array = MIN(nr_to_scan, PAGE_SIZE * 8 / sizeof (znode_t *));
++ int objects = 0;
++ int i = 0, j = 0;
++
++ zp_array = vmem_zalloc(max_array * sizeof (znode_t *), KM_SLEEP);
++
++ mutex_enter(&zfsvfs->z_znodes_lock);
++ while ((zp = list_head(&zfsvfs->z_all_znodes)) != NULL) {
++
++ if ((i++ > nr_to_scan) || (j >= max_array))
++ break;
++
++ ASSERT(list_link_active(&zp->z_link_node));
++ list_remove(&zfsvfs->z_all_znodes, zp);
++ list_insert_tail(&zfsvfs->z_all_znodes, zp);
++
++ /* Skip active znodes and .zfs entries */
++ if (MUTEX_HELD(&zp->z_lock) || zp->z_is_ctldir)
++ continue;
++
++ if (igrab(ZTOI(zp)) == NULL)
++ continue;
++
++ zp_array[j] = zp;
++ j++;
++ }
++ mutex_exit(&zfsvfs->z_znodes_lock);
++
++ for (i = 0; i < j; i++) {
++ zp = zp_array[i];
++
++ ASSERT3P(zp, !=, NULL);
++ d_prune_aliases(ZTOI(zp));
++
++ if (atomic_read(&ZTOI(zp)->i_count) == 1)
++ objects++;
++
++ zrele(zp);
++ }
++
++ vmem_free(zp_array, max_array * sizeof (znode_t *));
++
++ return (objects);
++}
++
+ /*
+ * The ARC has requested that the filesystem drop entries from the dentry
+ * and inode caches. This can occur when the ARC needs to free meta data
+@@ -1222,6 +1279,14 @@ zfs_prune(struct super_block *sb, unsigned long
nr_to_scan, int *objects)
+ *objects = (*shrinker->scan_objects)(shrinker, &sc);
+ #endif
+
++ /*
++ * Fall back to zfs_prune_aliases if kernel's shrinker did nothing
++ * due to dentry and inode caches being referenced by a task running
++ * in non-root memcg.
++ */
++ if (*objects == 0)
++ *objects = zfs_prune_aliases(zfsvfs, nr_to_scan);
++
+ zfs_exit(zfsvfs, FTAG);
+
+ dprintf_ds(zfsvfs->z_os->os_dsl_dataset,
+diff --git a/module/zfs/arc.c b/module/zfs/arc.c
+index
5c6e92f0f8b31dbcd569c92e645afb2e180b2deb..383aca2808d2c0aa8d09a9cdc8cfbfde4f6a6fc9
100644
+--- a/module/zfs/arc.c
++++ b/module/zfs/arc.c
+@@ -2597,7 +2597,7 @@ arc_space_consume(uint64_t space, arc_space_type_t type)
+ ARCSTAT_INCR(arcstat_bonus_size, space);
+ break;
+ case ARC_SPACE_DNODE:
+- ARCSTAT_INCR(arcstat_dnode_size, space);
++ aggsum_add(&arc_sums.arcstat_dnode_size, space);
+ break;
+ case ARC_SPACE_DBUF:
+ ARCSTAT_INCR(arcstat_dbuf_size, space);
+@@ -2643,7 +2643,7 @@ arc_space_return(uint64_t space, arc_space_type_t type)
+ ARCSTAT_INCR(arcstat_bonus_size, -space);
+ break;
+ case ARC_SPACE_DNODE:
+- ARCSTAT_INCR(arcstat_dnode_size, -space);
++ aggsum_add(&arc_sums.arcstat_dnode_size, -space);
+ break;
+ case ARC_SPACE_DBUF:
+ ARCSTAT_INCR(arcstat_dbuf_size, -space);
+@@ -4292,7 +4292,7 @@ arc_evict(void)
+ * target is not evictable or if they go over arc_dnode_limit.
+ */
+ int64_t prune = 0;
+- int64_t dn = wmsum_value(&arc_sums.arcstat_dnode_size);
++ int64_t dn = aggsum_value(&arc_sums.arcstat_dnode_size);
+ w = wt * (int64_t)(arc_meta >> 16) >> 16;
+ if (zfs_refcount_count(&arc_mru->arcs_size[ARC_BUFC_METADATA]) +
+ zfs_refcount_count(&arc_mfu->arcs_size[ARC_BUFC_METADATA]) -
+@@ -4775,12 +4775,19 @@ arc_is_overflowing(boolean_t use_reserve)
+ * in the ARC. In practice, that's in the tens of MB, which is low
+ * enough to be safe.
+ */
+- int64_t over = aggsum_lower_bound(&arc_sums.arcstat_size) -
++ int64_t arc_over = aggsum_lower_bound(&arc_sums.arcstat_size) -
+ arc_c - overflow / 2;
+ if (!use_reserve)
+ overflow /= 2;
+- return (over < 0 ? ARC_OVF_NONE :
+- over < overflow ? ARC_OVF_SOME : ARC_OVF_SEVERE);
++
++ int64_t dn_over = aggsum_lower_bound(&arc_sums.arcstat_dnode_size) -
++ arc_dnode_limit;
++
++ /* Always allow at least one block of overflow. */
++ if (arc_over < 0 && dn_over <= 0)
++ return (ARC_OVF_NONE);
++
++ return (arc_over < overflow ? ARC_OVF_SOME : ARC_OVF_SEVERE);
+ }
+
+ static abd_t *
+@@ -6938,7 +6945,7 @@ arc_kstat_update(kstat_t *ksp, int rw)
+ #if defined(COMPAT_FREEBSD11)
+ as->arcstat_other_size.value.ui64 =
+ wmsum_value(&arc_sums.arcstat_bonus_size) +
+- wmsum_value(&arc_sums.arcstat_dnode_size) +
++ aggsum_value(&arc_sums.arcstat_dnode_size) +
+ wmsum_value(&arc_sums.arcstat_dbuf_size);
+ #endif
+
+@@ -6980,7 +6987,7 @@ arc_kstat_update(kstat_t *ksp, int rw)
+ &as->arcstat_uncached_evictable_metadata);
+
+ as->arcstat_dnode_size.value.ui64 =
+- wmsum_value(&arc_sums.arcstat_dnode_size);
++ aggsum_value(&arc_sums.arcstat_dnode_size);
+ as->arcstat_bonus_size.value.ui64 =
+ wmsum_value(&arc_sums.arcstat_bonus_size);
+ as->arcstat_l2_hits.value.ui64 =
+@@ -7349,7 +7356,7 @@ arc_state_init(void)
+ wmsum_init(&arc_sums.arcstat_data_size, 0);
+ wmsum_init(&arc_sums.arcstat_metadata_size, 0);
+ wmsum_init(&arc_sums.arcstat_dbuf_size, 0);
+- wmsum_init(&arc_sums.arcstat_dnode_size, 0);
++ aggsum_init(&arc_sums.arcstat_dnode_size, 0);
+ wmsum_init(&arc_sums.arcstat_bonus_size, 0);
+ wmsum_init(&arc_sums.arcstat_l2_hits, 0);
+ wmsum_init(&arc_sums.arcstat_l2_misses, 0);
+@@ -7507,7 +7514,7 @@ arc_state_fini(void)
+ wmsum_fini(&arc_sums.arcstat_data_size);
+ wmsum_fini(&arc_sums.arcstat_metadata_size);
+ wmsum_fini(&arc_sums.arcstat_dbuf_size);
+- wmsum_fini(&arc_sums.arcstat_dnode_size);
++ aggsum_fini(&arc_sums.arcstat_dnode_size);
+ wmsum_fini(&arc_sums.arcstat_bonus_size);
+ wmsum_fini(&arc_sums.arcstat_l2_hits);
+ wmsum_fini(&arc_sums.arcstat_l2_misses);
diff --git a/debian/patches/series b/debian/patches/series
index 229027ff9..11a97debd 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -9,3 +9,4 @@
0009-arc-stat-summary-guard-access-to-freshly-introduced-.patch
0010-Fix-nfs_truncate_shares-without-etc-exports.d.patch
0011-zpool-status-tighten-bounds-for-noalloc-stat-availab.patch
+0012-backport-enforce-arc_dnode_limit-to-2.2.patch
--
2.39.5
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