4.19-stable patches

added patches:
	mbcache-avoid-nesting-of-cache-c_list_lock-under-bit-locks.patch

diff --git a/queue-4.19/mbcache-avoid-nesting-of-cache-c_list_lock-under-bit-locks.patch b/queue-4.19/mbcache-avoid-nesting-of-cache-c_list_lock-under-bit-locks.patch
new file mode 100644 (file)
index 0000000..9ab4e26
--- /dev/null
+++ b/queue-4.19/mbcache-avoid-nesting-of-cache-c_list_lock-under-bit-locks.patch
@@ -0,0 +1,66 @@
+From 5fc4cbd9fde5d4630494fd6ffc884148fb618087 Mon Sep 17 00:00:00 2001
+From: Jan Kara <jack@suse.cz>
+Date: Thu, 8 Sep 2022 11:10:32 +0200
+Subject: mbcache: Avoid nesting of cache->c_list_lock under bit locks
+
+From: Jan Kara <jack@suse.cz>
+
+commit 5fc4cbd9fde5d4630494fd6ffc884148fb618087 upstream.
+
+Commit 307af6c87937 ("mbcache: automatically delete entries from cache
+on freeing") started nesting cache->c_list_lock under the bit locks
+protecting hash buckets of the mbcache hash table in
+mb_cache_entry_create(). This causes problems for real-time kernels
+because there spinlocks are sleeping locks while bitlocks stay atomic.
+Luckily the nesting is easy to avoid by holding entry reference until
+the entry is added to the LRU list. This makes sure we cannot race with
+entry deletion.
+
+Cc: stable@kernel.org
+Fixes: 307af6c87937 ("mbcache: automatically delete entries from cache on freeing")
+Reported-by: Mike Galbraith <efault@gmx.de>
+Signed-off-by: Jan Kara <jack@suse.cz>
+Link: https://lore.kernel.org/r/20220908091032.10513-1-jack@suse.cz
+Signed-off-by: Theodore Ts'o <tytso@mit.edu>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ fs/mbcache.c |   17 ++++++++++-------
+ 1 file changed, 10 insertions(+), 7 deletions(-)
+
+--- a/fs/mbcache.c
++++ b/fs/mbcache.c
+@@ -89,8 +89,14 @@ int mb_cache_entry_create(struct mb_cach
+               return -ENOMEM;
+ 
+       INIT_LIST_HEAD(&entry->e_list);
+-      /* Initial hash reference */
+-      atomic_set(&entry->e_refcnt, 1);
++      /*
++       * We create entry with two references. One reference is kept by the
++       * hash table, the other reference is used to protect us from
++       * mb_cache_entry_delete_or_get() until the entry is fully setup. This
++       * avoids nesting of cache->c_list_lock into hash table bit locks which
++       * is problematic for RT.
++       */
++      atomic_set(&entry->e_refcnt, 2);
+       entry->e_key = key;
+       entry->e_value = value;
+       entry->e_flags = 0;
+@@ -106,15 +112,12 @@ int mb_cache_entry_create(struct mb_cach
+               }
+       }
+       hlist_bl_add_head(&entry->e_hash_list, head);
+-      /*
+-       * Add entry to LRU list before it can be found by
+-       * mb_cache_entry_delete() to avoid races
+-       */
++      hlist_bl_unlock(head);
+       spin_lock(&cache->c_list_lock);
+       list_add_tail(&entry->e_list, &cache->c_list);
+       cache->c_entry_count++;
+       spin_unlock(&cache->c_list_lock);
+-      hlist_bl_unlock(head);
++      mb_cache_entry_put(cache, entry);
+ 
+       return 0;
+ }

diff --git a/queue-4.19/series b/queue-4.19/series
index 39011e581a488fcb44564bb9e73376f2abfa7dfa..4019e034c08ed6a388b05f79c1b01625c6bb16a9 100644 (file)
--- a/queue-4.19/series
+++ b/queue-4.19/series
@@ -459,3 +459,4 @@ riscv-uaccess-fix-type-of-0-variable-on-error-in-get_user.patch
 ext4-don-t-allow-journal-inode-to-have-encrypt-flag.patch
 hfs-hfsplus-use-warn_on-for-sanity-check.patch
 hfs-hfsplus-avoid-warn_on-for-sanity-check-use-proper-error-handling.patch
+mbcache-avoid-nesting-of-cache-c_list_lock-under-bit-locks.patch