[PATCH AUTOSEL 4.19 66/84] fs: avoid softlockups in s_inodes iterators

Sasha Levin
2019-12-27T17:46:37Z

From: Eric Sandeen <sandeen@redhat.com>

[ Upstream commit 04646aebd30b99f2cfa0182435a2ec252fcb16d0 ]

Anything that walks all inodes on sb->s_inodes list without rescheduling
risks softlockups.

Previous efforts were made in 2 functions, see:

c27d82f fs/drop_caches.c: avoid softlockups in drop_pagecache_sb()
ac05fbb inode: don't softlockup when evicting inodes

but there hasn't been an audit of all walkers, so do that now. This
also consistently moves the cond_resched() calls to the bottom of each
loop in cases where it already exists.

One loop remains: remove_dquot_ref(), because I'm not quite sure how
to deal with that one w/o taking the i_lock.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/drop_caches.c | 2 +-
fs/inode.c | 7 +++++++
fs/notify/fsnotify.c | 1 +
fs/quota/dquot.c | 1 +
4 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index d31b6c72b476..dc1a1d5d825b 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -35,11 +35,11 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused)
spin_unlock(&inode->i_lock);
spin_unlock(&sb->s_inode_list_lock);

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

+ cond_resched();
spin_lock(&sb->s_inode_list_lock);
}
spin_unlock(&sb->s_inode_list_lock);
diff --git a/fs/inode.c b/fs/inode.c
index 5c63693326bb..9c50521c9fe4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -660,6 +660,7 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
struct inode *inode, *next;
LIST_HEAD(dispose);

+again:
spin_lock(&sb->s_inode_list_lock);
list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
spin_lock(&inode->i_lock);
@@ -682,6 +683,12 @@ int invalidate_inodes(struct super_block *sb, bool kill_dirty)
inode_lru_list_del(inode);
spin_unlock(&inode->i_lock);
list_add(&inode->i_lru, &dispose);
+ if (need_resched()) {
+ spin_unlock(&sb->s_inode_list_lock);
+ cond_resched();
+ dispose_list(&dispose);
+ goto again;
+ }
}
spin_unlock(&sb->s_inode_list_lock);

diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 170a733454f7..e8ee4263d7b2 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -90,6 +90,7 @@ void fsnotify_unmount_inodes(struct super_block *sb)

iput_inode = inode;

+ cond_resched();
spin_lock(&sb->s_inode_list_lock);
}
spin_unlock(&sb->s_inode_list_lock);
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 59b00d8db22c..57eed66e2c2d 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -980,6 +980,7 @@ static int add_dquot_ref(struct super_block *sb, int type)
* later.
*/
old_inode = inode;
+ cond_resched();
spin_lock(&sb->s_inode_list_lock);
}
spin_unlock(&sb->s_inode_list_lock);
--
2.20.1