| Message ID | 20181206161152.3290-1-jack@suse.cz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | vfs: Avoid softlockups in drop_pagecache_sb() | expand |
Is this staged in any existing tree? On Thu 06-12-18 17:11:52, Jan Kara wrote: > When superblock has lots of inodes without any pagecache (like is the case for > /proc), drop_pagecache_sb() will iterate through all of them without dropping > sb->s_inode_list_lock which can lead to softlockups. > > Fix the problem by going to the slow path and doing cond_resched() in case the > process needs rescheduling. FWIW the patch looks good to me. > Signed-off-by: Jan Kara <jack@suse.cz> Acked-by: Michal Hocko <mhocko@suse.com> > --- > fs/drop_caches.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/drop_caches.c b/fs/drop_caches.c > index 82377017130f..d31b6c72b476 100644 > --- a/fs/drop_caches.c > +++ b/fs/drop_caches.c > @@ -21,8 +21,13 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) > spin_lock(&sb->s_inode_list_lock); > list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { > spin_lock(&inode->i_lock); > + /* > + * We must skip inodes in unusual state. We may also skip > + * inodes without pages but we deliberately won't in case > + * we need to reschedule to avoid softlockups. > + */ > if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || > - (inode->i_mapping->nrpages == 0)) { > + (inode->i_mapping->nrpages == 0 && !need_resched())) { > spin_unlock(&inode->i_lock); > continue; > } > @@ -30,6 +35,7 @@ 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; > -- > 2.16.4
diff --git a/fs/drop_caches.c b/fs/drop_caches.c index 82377017130f..d31b6c72b476 100644 --- a/fs/drop_caches.c +++ b/fs/drop_caches.c @@ -21,8 +21,13 @@ static void drop_pagecache_sb(struct super_block *sb, void *unused) spin_lock(&sb->s_inode_list_lock); list_for_each_entry(inode, &sb->s_inodes, i_sb_list) { spin_lock(&inode->i_lock); + /* + * We must skip inodes in unusual state. We may also skip + * inodes without pages but we deliberately won't in case + * we need to reschedule to avoid softlockups. + */ if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) || - (inode->i_mapping->nrpages == 0)) { + (inode->i_mapping->nrpages == 0 && !need_resched())) { spin_unlock(&inode->i_lock); continue; } @@ -30,6 +35,7 @@ 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;
When superblock has lots of inodes without any pagecache (like is the case for /proc), drop_pagecache_sb() will iterate through all of them without dropping sb->s_inode_list_lock which can lead to softlockups. Fix the problem by going to the slow path and doing cond_resched() in case the process needs rescheduling. Signed-off-by: Jan Kara <jack@suse.cz> --- fs/drop_caches.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)