пн, 3 июн. 2019 г. в 01:02, Ronnie Sahlberg <lsahlber@xxxxxxxxxx>:
>
> We can not depend on the tcon->open_file_lock here since in multiuser mode
> we may have the same file/inode open via multiple different tcons.
>
> The current code is race prone and will crash if one user deletes a file
> at the same time a different user opens/create the file.
>
> RHBZ: 1580165
>
> Signed-off-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
> ---
> fs/cifs/cifsfs.c | 1 +
> fs/cifs/cifsglob.h | 5 +++++
> fs/cifs/file.c | 12 ++++++++++--
> 3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index f5fcd6360056..20cc4eaa7a49 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -1459,6 +1459,7 @@ init_cifs(void)
> GlobalTotalActiveXid = 0;
> GlobalMaxActiveXid = 0;
> spin_lock_init(&cifs_tcp_ses_lock);
> + spin_lock_init(&cifs_list_lock);
> spin_lock_init(&GlobalMid_Lock);
>
> cifs_lock_secret = get_random_u32();
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 334ff5f9c3f3..807b7cd7d48d 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1817,6 +1817,11 @@ GLOBAL_EXTERN struct list_head cifs_tcp_ses_list;
> * structure order is cifs_socket-->cifs_ses-->cifs_tcon-->cifs_file
> */
> GLOBAL_EXTERN spinlock_t cifs_tcp_ses_lock;
> +/*
> + * This lock protects the cifsInodeInfo->openFileList as well as
> + * cifsFileInfo->flist|tlist.
> + */
> +GLOBAL_EXTERN spinlock_t cifs_list_lock;
>
> #ifdef CONFIG_CIFS_DNOTIFY_EXPERIMENTAL /* unused temporarily */
> /* Outstanding dir notify requests */
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 06e27ac6d82c..8e96a5ae83bf 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -338,10 +338,12 @@ cifs_new_fileinfo(struct cifs_fid *fid, struct file *file,
> atomic_inc(&tcon->num_local_opens);
>
> /* if readable file instance put first in list*/
> + spin_lock(&cifs_list_lock);
> if (file->f_mode & FMODE_READ)
> list_add(&cfile->flist, &cinode->openFileList);
> else
> list_add_tail(&cfile->flist, &cinode->openFileList);
> + spin_unlock(&cifs_list_lock);
You are protecting cinode->openFileList here - this should be a lock
per inode structure.
> spin_unlock(&tcon->open_file_lock);
>
> if (fid->purge_cache)
> @@ -413,8 +415,10 @@ void _cifsFileInfo_put(struct cifsFileInfo *cifs_file, bool wait_oplock_handler)
> cifs_add_pending_open_locked(&fid, cifs_file->tlink, &open);
>
> /* remove it from the lists */
> + spin_lock(&cifs_list_lock);
> list_del(&cifs_file->flist);
The same here - inode lock.
> list_del(&cifs_file->tlist);
It is a list per tcon - existing tcon lock is protecting here.
> + spin_unlock(&cifs_list_lock);
> atomic_dec(&tcon->num_local_opens);
>
> if (list_empty(&cifsi->openFileList)) {
> @@ -1459,8 +1463,10 @@ void
> cifs_move_llist(struct list_head *source, struct list_head *dest)
> {
> struct list_head *li, *tmp;
> + spin_lock(&cifs_list_lock);
> list_for_each_safe(li, tmp, source)
> list_move(li, dest);
> + spin_unlock(&cifs_list_lock);
> }
>
> void
> @@ -1469,7 +1475,9 @@ cifs_free_llist(struct list_head *llist)
> struct cifsLockInfo *li, *tmp;
> list_for_each_entry_safe(li, tmp, llist, llist) {
> cifs_del_lock_waiters(li);
> + spin_lock(&cifs_list_lock);
> list_del(&li->llist);
> + spin_unlock(&cifs_list_lock);
> kfree(li);
> }
> }
Above two functions operate on lists of locks of inode's files - all
protected by cifsi->lock_sem.
> @@ -1950,9 +1958,9 @@ cifs_get_writable_file(struct cifsInodeInfo *cifs_inode, bool fsuid_only,
> return 0;
> }
>
> - spin_lock(&tcon->open_file_lock);
> + spin_lock(&cifs_list_lock);
> list_move_tail(&inv_file->flist, &cifs_inode->openFileList);
> - spin_unlock(&tcon->open_file_lock);
> + spin_unlock(&cifs_list_lock);
inode lock.
> cifsFileInfo_put(inv_file);
> ++refind;
> inv_file = NULL;
> --
> 2.13.6
>
What is the reasoning under using a global spin lock? Global locking
is always a source of performance problems and should be avoided as
much as possible.
--
Best regards,
Pavel Shilovsky
