fs: avoid softlockups in s_inodes iterators

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>

diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index d31b6c7..dc1a1d5 100644 (file)
--- 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 fef457a..96d62d9 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -676,6 +676,7 @@ 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);
@@ -698,6 +699,12 @@ 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 3e77b72..6c902c0 100644 (file)
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -77,6 +77,7 @@ static 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 b0688c0..b6a4f69 100644 (file)
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -984,6 +984,7 @@ 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);