Re: [PATCH 2/2 v2] ceph: use a xarray to record all the opened files for each inode

On Mon, 2022-11-14 at 13:19 +0800, xiubli@redhat.com wrote:

From: Xiubo Li xiubli@redhat.com

When releasing the file locks the fl->fl_file memory could be already released by another thread in filp_close(), so we couldn't depend on fl->fl_file to get the inode. Just use a xarray to record the opened files for each inode.

Cc: stable@vger.kernel.org URL: https://tracker.ceph.com/issues/57986 Signed-off-by: Xiubo Li xiubli@redhat.com

---

fs/ceph/file.c | 9 +++++++++ fs/ceph/inode.c | 4 ++++ fs/ceph/locks.c | 17 ++++++++++++++++- fs/ceph/super.h | 4 ++++ 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c index 85afcbbb5648..cb4a9c52df27 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -231,6 +231,13 @@ static int ceph_init_file_info(struct inode *inode, struct file *file, fi->flags |= CEPH_F_SYNC; file->private_data = fi;

• ret = xa_insert(&ci->i_opened_files, (unsigned long)file,
  

• 		CEPH_FILP_AVAILABLE, GFP_KERNEL);
  

• if (ret) {
  

• 	kmem_cache_free(ceph_file_cachep, fi);
  

• 	return ret;
  

• }
  

  }

ceph_get_fmode(ci, fmode, 1); @@ -932,6 +939,8 @@ int ceph_release(struct inode *inode, struct file *file) dout("release inode %p regular file %p\n", inode, file); WARN_ON(!list_empty(&fi->rw_contexts));

• xa_erase(&ci->i_opened_files, (unsigned long)file);
  

• ceph_fscache_unuse_cookie(inode, file->f_mode & FMODE_WRITE); ceph_put_fmode(ci, fi->fmode, 1);

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c index 77b0cd9af370..554450838e44 100644 --- a/fs/ceph/inode.c +++ b/fs/ceph/inode.c @@ -619,6 +619,8 @@ struct inode *ceph_alloc_inode(struct super_block *sb) INIT_LIST_HEAD(&ci->i_unsafe_iops); spin_lock_init(&ci->i_unsafe_lock);

• xa_init(&ci->i_opened_files);
• ci->i_snap_realm = NULL; INIT_LIST_HEAD(&ci->i_snap_realm_item); INIT_LIST_HEAD(&ci->i_snap_flush_item);

@@ -637,6 +639,8 @@ void ceph_free_inode(struct inode *inode) { struct ceph_inode_info *ci = ceph_inode(inode);

• xa_destroy(&ci->i_opened_files);
• kfree(ci->i_symlink);

#ifdef CONFIG_FS_ENCRYPTION kfree(ci->fscrypt_auth); diff --git a/fs/ceph/locks.c b/fs/ceph/locks.c index d8385dd0076e..a176a30badd0 100644 --- a/fs/ceph/locks.c +++ b/fs/ceph/locks.c @@ -42,9 +42,10 @@ static void ceph_fl_copy_lock(struct file_lock *dst, struct file_lock *src) static void ceph_fl_release_lock(struct file_lock *fl) {

• struct ceph_file_info *fi = fl->fl_file->private_data; struct inode *inode = fl->fl_u.ceph_fl.fl_inode; struct ceph_inode_info *ci;

• struct ceph_file_info *fi;
• void *val;

/* * If inode is NULL it should be a request file_lock, @@ -54,6 +55,20 @@ static void ceph_fl_release_lock(struct file_lock *fl) return; ci = ceph_inode(inode);

• /*

• * For Posix-style locks, it may race between filp_close()s,
  

• * and it's possible that the 'file' memory pointed by
  

• * 'fl->fl_file' has been released. If so just skip it.
  

• */
  

• rcu_read_lock();
• val = xa_load(&ci->i_opened_files, (unsigned long)fl->fl_file);
• if (val == CEPH_FILP_AVAILABLE) {

• fi = fl->fl_file->private_data;
  

• atomic_dec(&fi->num_locks);
  

Don't you need to remove the old atomic_dec from this function if you move it here?

• }
• rcu_read_unlock();
• if (atomic_dec_and_test(&ci->i_filelock_ref)) { /* clear error when all locks are released */ spin_lock(&ci->i_ceph_lock);

diff --git a/fs/ceph/super.h b/fs/ceph/super.h index 7b75a84ba48d..b3e89192cbec 100644 --- a/fs/ceph/super.h +++ b/fs/ceph/super.h @@ -329,6 +329,8 @@ struct ceph_inode_xattrs_info { u64 version, index_version; }; +#define CEPH_FILP_AVAILABLE xa_mk_value(1)

/*

• Ceph inode.

*/ @@ -434,6 +436,8 @@ struct ceph_inode_info { struct list_head i_unsafe_iops; /* uncommitted mds inode ops */ spinlock_t i_unsafe_lock;

• struct xarray i_opened_files;
• union { struct ceph_snap_realm *i_snap_realm; /* snap realm (if caps) */ struct ceph_snapid_map *i_snapid_map; /* snapid -> dev_t */

This looks like it'll work, but it's a lot of extra work, having to track this extra xarray just on the off chance that one of these fd's might have file locks. The num_locks field is only checked in one place in ceph_get_caps.

Here's what I'd recommend instead:

Have ceph_get_caps look at the lists in inode->i_flctx and see whether any of its locks have an fl_file that matches the @filp argument in that function. Most inodes never get any file locks, so in most cases this will turn out to just be a NULL pointer check for i_flctx anyway.

Then you can just remove the num_locks field and call the new helper from ceph_get_caps instead. I'll send along a proposed patch for the helper in a bit.