[PATCH 03/11] vfs: Use dlock list for superblock's inode list

From: Dave Chinner
Date: Wed Dec 06 2023 - 01:07:39 EST

From: Waiman Long <longman@xxxxxxxxxx>

[dchinner: original commit message preserved]

When many threads are trying to add or delete inode to or from
a superblock's s_inodes list, spinlock contention on the list can
become a performance bottleneck.

This patch changes the s_inodes field to become a dlock list which
is a distributed set of lists with per-list spinlocks. As a result,
the following superblock inode list (sb->s_inodes) iteration functions
in vfs are also being modified:

1. iterate_bdevs()
2. drop_pagecache_sb()
3. evict_inodes()
4. invalidate_inodes()
5. fsnotify_unmount_inodes()
6. add_dquot_ref()
7. remove_dquot_ref()

With an exit microbenchmark that creates a large number of threads,
attachs many inodes to them in procfs and then exits. The runtimes of
that microbenchmark with various number of threads before and after
the patch on a 4-socket Intel E7-8867 v3 system (64 cores, 128 threads)
on a 4.19-rc3 based kernel were as follows:

# of threads Elapsed/Sys Time Elapsed/Sys Time Speedup
Unpatched Kernel Patched Kernel
------------ ---------------- ---------------- -------
1000 59.17s/123m09.8s 18.90s/24m44.5s 3.13
1200 73.20s/151m24.1s 27.54s/50m05.3s 2.66
1400 102.04s/212m00.9s 36.75s/68m26.7s 2.78
1600 131.13s/272m52.4s 50.16s/94m23.7s 2.61

[dchinner: forward port, add new inode list traversals, etc]
[dchinner: scalability results on current TOT XFS]

With 400k inodes per thread concurrent directory traversal workload,
scalability improves at >=16 threads on 6.7-rc4 on XFS. We only test
XFS here as it is the only filesystem that demonstrates sufficient
internal scalability for the superblock inode list to be a
scalability bottleneck.

Table contains test runtime in seconds; perfect scalability is
demonstrated by the runtime staying constant as thread count goes up.

Threads 6.4-rc7 patched
------- ------- -------
2 11.673 11.158
4 9.665 9.444
8 10.622 9.275
16 12.148 9.508
32 20.518 10.308

Unpatched kernel profile at 32 threads:

- 95.45% vfs_fstatat
- 95.00% vfs_statx
- 91.00% filename_lookup
- 90.90% path_lookupat
- 90.40% walk_component
- 89.05% lookup_slow
- 88.95% __lookup_slow
- 86.38% xfs_vn_lookup
- 84.05% xfs_lookup
- 78.82% xfs_iget
- 72.58% xfs_setup_inode
- 72.54% inode_sb_list_add
- 71.12% _raw_spin_lock
- 71.09% do_raw_spin_lock
- 68.85% __pv_queued_spin_lock_slowpath

Patched kernel profile at 32 threads - the biggest single point of
contention is now the dentry cache LRU via dput():

- 21.59% 0.25% [kernel] [k] dput
- 21.34% dput
- 19.93% retain_dentry
- d_lru_add
- 19.82% list_lru_add
- 14.62% _raw_spin_lock
- 14.47% do_raw_spin_lock
10.89% __pv_queued_spin_lock_slowpath
1.78% __list_add_valid_or_report
- 0.81% _raw_spin_unlock
- do_raw_spin_unlock
0.77% __raw_callee_save___pv_queued_spin_unlock
- 0.79% _raw_spin_unlock
- 0.78% do_raw_spin_unlock
0.67% __raw_callee_save___pv_queued_spin_unlock

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
block/bdev.c | 24 ++++++++----------------
fs/drop_caches.c | 9 ++++-----
fs/gfs2/ops_fstype.c | 21 +++++++++++----------
fs/inode.c | 37 ++++++++++++++++---------------------
fs/notify/fsnotify.c | 12 ++++++------
fs/quota/dquot.c | 22 ++++++----------------
fs/super.c | 13 +++++++------
include/linux/fs.h | 8 ++++----
security/landlock/fs.c | 25 ++++++-------------------
9 files changed, 68 insertions(+), 103 deletions(-)

diff --git a/block/bdev.c b/block/bdev.c
index 750aec178b6a..07135fd6fda4 100644
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -437,11 +437,11 @@ long nr_blockdev_pages(void)
{
struct inode *inode;
long ret = 0;
+ DEFINE_DLOCK_LIST_ITER(iter, &blockdev_superblock->s_inodes);

- spin_lock(&blockdev_superblock->s_inode_list_lock);
- list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list)
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
ret += inode->i_mapping->nrpages;
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
+ }

return ret;
}
@@ -1032,9 +1032,9 @@ EXPORT_SYMBOL_GPL(bdev_mark_dead);
void sync_bdevs(bool wait)
{
struct inode *inode, *old_inode = NULL;
+ DEFINE_DLOCK_LIST_ITER(iter, &blockdev_superblock->s_inodes);

- spin_lock(&blockdev_superblock->s_inode_list_lock);
- list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
struct address_space *mapping = inode->i_mapping;
struct block_device *bdev;

@@ -1046,15 +1046,8 @@ void sync_bdevs(bool wait)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
- /*
- * We hold a reference to 'inode' so it couldn't have been
- * removed from s_inodes list while we dropped the
- * s_inode_list_lock We cannot iput the inode now as we can
- * be holding the last reference and we cannot iput it under
- * s_inode_list_lock. So we keep the reference and iput it
- * later.
- */
+ dlock_list_unlock(&iter);
+
iput(old_inode);
old_inode = inode;
bdev = I_BDEV(inode);
@@ -1075,9 +1068,8 @@ void sync_bdevs(bool wait)
}
mutex_unlock(&bdev->bd_disk->open_mutex);

- spin_lock(&blockdev_superblock->s_inode_list_lock);
+ dlock_list_relock(&iter);
}
- spin_unlock(&blockdev_superblock->s_inode_list_lock);
iput(old_inode);
}

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index b9575957a7c2..3596d0a7c0da 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -19,9 +19,9 @@ int sysctl_drop_caches;
static void drop_pagecache_sb(struct super_block *sb, void *unused)
{
struct inode *inode, *toput_inode = NULL;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
spin_lock(&inode->i_lock);
/*
* We must skip inodes in unusual state. We may also skip
@@ -35,16 +35,15 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ dlock_list_unlock(&iter);

invalidate_mapping_pages(inode->i_mapping, 0, -1);
iput(toput_inode);
toput_inode = inode;

cond_resched();
- spin_lock(&sb->s_inode_list_lock);
+ dlock_list_relock(&iter);
}
- spin_unlock(&sb->s_inode_list_lock);
iput(toput_inode);
}

diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c
index b108c5d26839..1105710482e7 100644
--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -1738,22 +1738,24 @@ static int gfs2_meta_init_fs_context(struct fs_context *fc)
* attempt will time out. Since inodes are evicted sequentially, this can add
* up quickly.
*
- * Function evict_inodes() tries to keep the s_inode_list_lock list locked over
- * a long time, which prevents other inodes from being evicted concurrently.
- * This precludes the cooperative behavior we are looking for. This special
- * version of evict_inodes() avoids that.
- *
* Modeled after drop_pagecache_sb().
+ *
+ * XXX(dgc): this is particularly awful. With the dlist for inodes, concurrent
+ * access to the inode list can occur and evict_inodes() will drop the per-cpu
+ * list lock if the CPU needs rescheduling. Hence if this exists just because
+ * evict_inodes() holds the s_inode_list_lock for long periods preventing
+ * concurrent inode eviction work from being done, this can probably go away
+ * entirely now.
*/
static void gfs2_evict_inodes(struct super_block *sb)
{
struct inode *inode, *toput_inode = NULL;
struct gfs2_sbd *sdp = sb->s_fs_info;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);

set_bit(SDF_EVICTING, &sdp->sd_flags);

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) &&
!need_resched()) {
@@ -1762,15 +1764,14 @@ static void gfs2_evict_inodes(struct super_block *sb)
}
atomic_inc(&inode->i_count);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ dlock_list_unlock(&iter);

iput(toput_inode);
toput_inode = inode;

cond_resched();
- spin_lock(&sb->s_inode_list_lock);
+ dlock_list_relock(&iter);
}
- spin_unlock(&sb->s_inode_list_lock);
iput(toput_inode);
}

diff --git a/fs/inode.c b/fs/inode.c
index 17c50a75514f..3426691fa305 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -30,7 +30,7 @@
* inode->i_state, inode->i_hash, __iget(), inode->i_io_list
* Inode LRU list locks protect:
* inode->i_sb->s_inode_lru, inode->i_lru
- * inode->i_sb->s_inode_list_lock protects:
+ * inode->i_sb->s_inodes->head->lock protects:
* inode->i_sb->s_inodes, inode->i_sb_list
* bdi->wb.list_lock protects:
* bdi->wb.b_{dirty,io,more_io,dirty_time}, inode->i_io_list
@@ -39,7 +39,7 @@
*
* Lock ordering:
*
- * inode->i_sb->s_inode_list_lock
+ * inode->i_sb->s_inodes->head->lock
* inode->i_lock
* Inode LRU list locks
*
@@ -47,7 +47,7 @@
* inode->i_lock
*
* inode_hash_lock
- * inode->i_sb->s_inode_list_lock
+ * inode->i_sb->s_inodes->head->lock
* inode->i_lock
*
* iunique_lock
@@ -423,7 +423,7 @@ void inode_init_once(struct inode *inode)
INIT_LIST_HEAD(&inode->i_io_list);
INIT_LIST_HEAD(&inode->i_wb_list);
INIT_LIST_HEAD(&inode->i_lru);
- INIT_LIST_HEAD(&inode->i_sb_list);
+ init_dlock_list_node(&inode->i_sb_list);
__address_space_init_once(&inode->i_data);
i_size_ordered_init(inode);
}
@@ -492,19 +492,14 @@ static void inode_lru_list_del(struct inode *inode)
*/
void inode_sb_list_add(struct inode *inode)
{
- spin_lock(&inode->i_sb->s_inode_list_lock);
- list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
- spin_unlock(&inode->i_sb->s_inode_list_lock);
+ dlock_lists_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
}
EXPORT_SYMBOL_GPL(inode_sb_list_add);

static inline void inode_sb_list_del(struct inode *inode)
{
- if (!list_empty(&inode->i_sb_list)) {
- spin_lock(&inode->i_sb->s_inode_list_lock);
- list_del_init(&inode->i_sb_list);
- spin_unlock(&inode->i_sb->s_inode_list_lock);
- }
+ if (!list_empty(&inode->i_sb_list.list))
+ dlock_lists_del(&inode->i_sb_list);
}

static unsigned long hash(struct super_block *sb, unsigned long hashval)
@@ -713,11 +708,12 @@ static void dispose_list(struct list_head *head)
void evict_inodes(struct super_block *sb)
{
struct inode *inode;
+ struct dlock_list_iter iter;
LIST_HEAD(dispose);

again:
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ init_dlock_list_iter(&iter, &sb->s_inodes);
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
if (atomic_read(&inode->i_count))
continue;

@@ -738,13 +734,12 @@ void evict_inodes(struct super_block *sb)
* bit so we don't livelock.
*/
if (need_resched()) {
- spin_unlock(&sb->s_inode_list_lock);
+ dlock_list_unlock(&iter);
cond_resched();
dispose_list(&dispose);
goto again;
}
}
- spin_unlock(&sb->s_inode_list_lock);

dispose_list(&dispose);
}
@@ -759,11 +754,12 @@ EXPORT_SYMBOL_GPL(evict_inodes);
void invalidate_inodes(struct super_block *sb)
{
struct inode *inode;
+ struct dlock_list_iter iter;
LIST_HEAD(dispose);

again:
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ init_dlock_list_iter(&iter, &sb->s_inodes);
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
spin_lock(&inode->i_lock);
if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
spin_unlock(&inode->i_lock);
@@ -779,13 +775,12 @@ void invalidate_inodes(struct super_block *sb)
spin_unlock(&inode->i_lock);
list_add(&inode->i_lru, &dispose);
if (need_resched()) {
- spin_unlock(&sb->s_inode_list_lock);
+ dlock_list_unlock(&iter);
cond_resched();
dispose_list(&dispose);
goto again;
}
}
- spin_unlock(&sb->s_inode_list_lock);

dispose_list(&dispose);
}
@@ -1232,7 +1227,7 @@ struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
* Add inode to the sb list if it's not already. It has I_NEW at this
* point, so it should be safe to test i_sb_list locklessly.
*/
- if (list_empty(&inode->i_sb_list))
+ if (list_empty(&inode->i_sb_list.list))
inode_sb_list_add(inode);
unlock:
spin_unlock(&inode_hash_lock);
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 7974e91ffe13..15e3769e76f5 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -33,14 +33,15 @@ void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
* @sb: superblock being unmounted.
*
* Called during unmount with no locks held, so needs to be safe against
- * concurrent modifiers. We temporarily drop sb->s_inode_list_lock and CAN block.
+ * concurrent modifiers. We temporarily drop sb->s_inodes list lock and CAN
+ * block.
*/
static void fsnotify_unmount_inodes(struct super_block *sb)
{
struct inode *inode, *iput_inode = NULL;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
/*
* We cannot __iget() an inode in state I_FREEING,
* I_WILL_FREE, or I_NEW which is fine because by that point
@@ -68,7 +69,7 @@ static void fsnotify_unmount_inodes(struct super_block *sb)

__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ dlock_list_unlock(&iter);

iput(iput_inode);

@@ -80,9 +81,8 @@ static void fsnotify_unmount_inodes(struct super_block *sb)
iput_inode = inode;

cond_resched();
- spin_lock(&sb->s_inode_list_lock);
+ dlock_list_relock(&iter);
}
- spin_unlock(&sb->s_inode_list_lock);

iput(iput_inode);
}
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 58b5de081b57..e873dcbe6feb 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -1024,13 +1024,13 @@ static int dqinit_needed(struct inode *inode, int type)
static int add_dquot_ref(struct super_block *sb, int type)
{
struct inode *inode, *old_inode = NULL;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);
#ifdef CONFIG_QUOTA_DEBUG
int reserved = 0;
#endif
int err = 0;

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
!atomic_read(&inode->i_writecount) ||
@@ -1040,7 +1040,7 @@ static int add_dquot_ref(struct super_block *sb, int type)
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(&sb->s_inode_list_lock);
+ dlock_list_unlock(&iter);

#ifdef CONFIG_QUOTA_DEBUG
if (unlikely(inode_get_rsv_space(inode) > 0))
@@ -1053,19 +1053,10 @@ static int add_dquot_ref(struct super_block *sb, int type)
goto out;
}

- /*
- * We hold a reference to 'inode' so it couldn't have been
- * removed from s_inodes list while we dropped the
- * s_inode_list_lock. We cannot iput the inode now as we can be
- * holding the last reference and we cannot iput it under
- * s_inode_list_lock. So we keep the reference and iput it
- * later.
- */
old_inode = inode;
cond_resched();
- spin_lock(&sb->s_inode_list_lock);
+ dlock_list_relock(&iter);
}
- spin_unlock(&sb->s_inode_list_lock);
iput(old_inode);
out:
#ifdef CONFIG_QUOTA_DEBUG
@@ -1081,12 +1072,12 @@ static int add_dquot_ref(struct super_block *sb, int type)
static void remove_dquot_ref(struct super_block *sb, int type)
{
struct inode *inode;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);
#ifdef CONFIG_QUOTA_DEBUG
int reserved = 0;
#endif

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
/*
* We have to scan also I_NEW inodes because they can already
* have quota pointer initialized. Luckily, we need to touch
@@ -1108,7 +1099,6 @@ static void remove_dquot_ref(struct super_block *sb, int type)
}
spin_unlock(&dq_data_lock);
}
- spin_unlock(&sb->s_inode_list_lock);
#ifdef CONFIG_QUOTA_DEBUG
if (reserved) {
printk(KERN_WARNING "VFS (%s): Writes happened after quota"
diff --git a/fs/super.c b/fs/super.c
index 076392396e72..61c19e3f06d8 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -303,6 +303,7 @@ static void destroy_unused_super(struct super_block *s)
super_unlock_excl(s);
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
+ free_dlock_list_heads(&s->s_inodes);
security_sb_free(s);
put_user_ns(s->s_user_ns);
kfree(s->s_subtype);
@@ -367,8 +368,6 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_roots);
mutex_init(&s->s_sync_lock);
- INIT_LIST_HEAD(&s->s_inodes);
- spin_lock_init(&s->s_inode_list_lock);
INIT_LIST_HEAD(&s->s_inodes_wb);
spin_lock_init(&s->s_inode_wblist_lock);

@@ -383,6 +382,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags,
s->s_time_min = TIME64_MIN;
s->s_time_max = TIME64_MAX;

+ if (alloc_dlock_list_heads(&s->s_inodes))
+ goto fail;
+
s->s_shrink = shrinker_alloc(SHRINKER_NUMA_AWARE | SHRINKER_MEMCG_AWARE,
"sb-%s", type->name);
if (!s->s_shrink)
@@ -695,7 +697,7 @@ void generic_shutdown_super(struct super_block *sb)
if (sop->put_super)
sop->put_super(sb);

- if (CHECK_DATA_CORRUPTION(!list_empty(&sb->s_inodes),
+ if (CHECK_DATA_CORRUPTION(!dlock_lists_empty(&sb->s_inodes),
"VFS: Busy inodes after unmount of %s (%s)",
sb->s_id, sb->s_type->name)) {
/*
@@ -704,14 +706,13 @@ void generic_shutdown_super(struct super_block *sb)
* iput_final() or such crashes cleanly.
*/
struct inode *inode;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
inode->i_op = VFS_PTR_POISON;
inode->i_sb = VFS_PTR_POISON;
inode->i_mapping = VFS_PTR_POISON;
}
- spin_unlock(&sb->s_inode_list_lock);
}
}
/*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 98b7a7a8c42e..bb35591733f1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -43,6 +43,7 @@
#include <linux/cred.h>
#include <linux/mnt_idmapping.h>
#include <linux/slab.h>
+#include <linux/dlock-list.h>

#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -702,7 +703,7 @@ struct inode {
u16 i_wb_frn_history;
#endif
struct list_head i_lru; /* inode LRU list */
- struct list_head i_sb_list;
+ struct dlock_list_node i_sb_list;
struct list_head i_wb_list; /* backing dev writeback list */
union {
struct hlist_head i_dentry;
@@ -1315,9 +1316,8 @@ struct super_block {
*/
int s_stack_depth;

- /* s_inode_list_lock protects s_inodes */
- spinlock_t s_inode_list_lock ____cacheline_aligned_in_smp;
- struct list_head s_inodes; /* all inodes */
+ /* The internal per-list locks protect s_inodes */
+ struct dlock_list_heads s_inodes; /* all inodes */

spinlock_t s_inode_wblist_lock;
struct list_head s_inodes_wb; /* writeback inodes */
diff --git a/security/landlock/fs.c b/security/landlock/fs.c
index bc7c126deea2..4269d9938c09 100644
--- a/security/landlock/fs.c
+++ b/security/landlock/fs.c
@@ -844,12 +844,12 @@ static void hook_inode_free_security(struct inode *const inode)
static void hook_sb_delete(struct super_block *const sb)
{
struct inode *inode, *prev_inode = NULL;
+ DEFINE_DLOCK_LIST_ITER(iter, &sb->s_inodes);

if (!landlock_initialized)
return;

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+ dlist_for_each_entry(inode, &iter, i_sb_list) {
struct landlock_object *object;

/* Only handles referenced inodes. */
@@ -883,6 +883,7 @@ static void hook_sb_delete(struct super_block *const sb)
/* Keeps a reference to this inode until the next loop walk. */
__iget(inode);
spin_unlock(&inode->i_lock);
+ dlock_list_unlock(&iter);

/*
* If there is no concurrent release_inode() ongoing, then we
@@ -917,25 +918,11 @@ static void hook_sb_delete(struct super_block *const sb)
rcu_read_unlock();
}

- if (prev_inode) {
- /*
- * At this point, we still own the __iget() reference
- * that we just set in this loop walk. Therefore we
- * can drop the list lock and know that the inode won't
- * disappear from under us until the next loop walk.
- */
- spin_unlock(&sb->s_inode_list_lock);
- /*
- * We can now actually put the inode reference from the
- * previous loop walk, which is not needed anymore.
- */
- iput(prev_inode);
- cond_resched();
- spin_lock(&sb->s_inode_list_lock);
- }
+ iput(prev_inode);
prev_inode = inode;
+ cond_resched();
+ dlock_list_relock(&iter);
}
- spin_unlock(&sb->s_inode_list_lock);

/* Puts the inode reference from the last loop walk, if any. */
if (prev_inode)
--
2.42.0