Re: [PATCH v3] CIFS: Do not kmalloc under the flocks spinlock

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merged into cifs-2.6.git

On Mon, Mar 5, 2012 at 12:39 AM, Pavel Shilovsky <piastry@xxxxxxxxxxx> wrote:
> Reorganize the code to make the memory already allocated before
> spinlock'ed loop.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> Signed-off-by: Pavel Shilovsky <piastry@xxxxxxxxxxx>
> ---
>  fs/cifs/file.c |   69 +++++++++++++++++++++++++++++++++++++++++++++----------
>  1 files changed, 56 insertions(+), 13 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 4dd9283..5e64748 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -920,16 +920,26 @@ cifs_push_mandatory_locks(struct cifsFileInfo *cfile)
>        for (lockp = &inode->i_flock; *lockp != NULL; \
>             lockp = &(*lockp)->fl_next)
>
> +struct lock_to_push {
> +       struct list_head llist;
> +       __u64 offset;
> +       __u64 length;
> +       __u32 pid;
> +       __u16 netfid;
> +       __u8 type;
> +};
> +
>  static int
>  cifs_push_posix_locks(struct cifsFileInfo *cfile)
>  {
>        struct cifsInodeInfo *cinode = CIFS_I(cfile->dentry->d_inode);
>        struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
>        struct file_lock *flock, **before;
> -       struct cifsLockInfo *lck, *tmp;
> +       unsigned int count = 0, i = 0;
>        int rc = 0, xid, type;
> +       struct list_head locks_to_send, *el;
> +       struct lock_to_push *lck, *tmp;
>        __u64 length;
> -       struct list_head locks_to_send;
>
>        xid = GetXid();
>
> @@ -940,29 +950,55 @@ cifs_push_posix_locks(struct cifsFileInfo *cfile)
>                return rc;
>        }
>
> +       lock_flocks();
> +       cifs_for_each_lock(cfile->dentry->d_inode, before) {
> +               if ((*before)->fl_flags & FL_POSIX)
> +                       count++;
> +       }
> +       unlock_flocks();
> +
>        INIT_LIST_HEAD(&locks_to_send);
>
> +       /*
> +        * Allocating count locks is enough because no locks can be added to
> +        * the list while we are holding cinode->lock_mutex that protects
> +        * locking operations of this inode.
> +        */
> +       for (; i < count; i++) {
> +               lck = kmalloc(sizeof(struct lock_to_push), GFP_KERNEL);
> +               if (!lck) {
> +                       rc = -ENOMEM;
> +                       goto err_out;
> +               }
> +               list_add_tail(&lck->llist, &locks_to_send);
> +       }
> +
> +       i = 0;
> +       el = locks_to_send.next;
>        lock_flocks();
>        cifs_for_each_lock(cfile->dentry->d_inode, before) {
> +               if (el == &locks_to_send) {
> +                       /* something is really wrong */
> +                       cERROR(1, "Can't push all brlocks!");
> +                       break;
> +               }
>                flock = *before;
> +               if ((flock->fl_flags & FL_POSIX) == 0)
> +                       continue;
>                length = 1 + flock->fl_end - flock->fl_start;
>                if (flock->fl_type == F_RDLCK || flock->fl_type == F_SHLCK)
>                        type = CIFS_RDLCK;
>                else
>                        type = CIFS_WRLCK;
> -
> -               lck = cifs_lock_init(flock->fl_start, length, type,
> -                                    cfile->netfid);
> -               if (!lck) {
> -                       rc = -ENOMEM;
> -                       goto send_locks;
> -               }
> +               lck = list_entry(el, struct lock_to_push, llist);
>                lck->pid = flock->fl_pid;
> -
> -               list_add_tail(&lck->llist, &locks_to_send);
> +               lck->netfid = cfile->netfid;
> +               lck->length = length;
> +               lck->type = type;
> +               lck->offset = flock->fl_start;
> +               i++;
> +               el = el->next;
>        }
> -
> -send_locks:
>        unlock_flocks();
>
>        list_for_each_entry_safe(lck, tmp, &locks_to_send, llist) {
> @@ -979,11 +1015,18 @@ send_locks:
>                kfree(lck);
>        }
>
> +out:
>        cinode->can_cache_brlcks = false;
>        mutex_unlock(&cinode->lock_mutex);
>
>        FreeXid(xid);
>        return rc;
> +err_out:
> +       list_for_each_entry_safe(lck, tmp, &locks_to_send, llist) {
> +               list_del(&lck->llist);
> +               kfree(lck);
> +       }
> +       goto out;
>  }
>
>  static int
> --
> 1.7.1
>
> --
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-- 
Thanks,

Steve
--
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