Messages in this thread | | | Date | Tue, 7 Apr 2009 16:06:35 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH -V2 12/13] fsnotify: handle filesystem unmounts with fsnotify marks |
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On Fri, 27 Mar 2009 16:06:11 -0400 Eric Paris <eparis@redhat.com> wrote:
> When an fs is unmounted with an fsnotify mark entry attached to one of its > inodes we need to destroy that mark entry and we also (like inotify) send > an unmount event. > > > ... > > +/** > + * fsnotify_unmount_inodes - an sb is unmounting. handle any watched inodes. > + * @list: list of inodes being unmounted (sb->s_inodes) > + * > + * Called with inode_lock held, protecting the unmounting super block's list > + * of inodes, and with iprune_mutex held, keeping shrink_icache_memory() at bay. > + * We temporarily drop inode_lock, however, and CAN block. > + */ > +void fsnotify_unmount_inodes(struct list_head *list) > +{ > + struct inode *inode, *next_i, *need_iput = NULL; > + > + list_for_each_entry_safe(inode, next_i, list, i_sb_list) { > + struct inode *need_iput_tmp; > + > + /* > + * If i_count is zero, the inode cannot have any watches and > + * doing an __iget/iput with MS_ACTIVE clear would actually > + * evict all inodes with zero i_count from icache which is > + * unnecessarily violent and may in fact be illegal to do. > + */ > + if (!atomic_read(&inode->i_count)) > + continue; > + > + /* > + * We cannot __iget() an inode in state I_CLEAR, I_FREEING, or > + * I_WILL_FREE which is fine because by that point the inode > + * cannot have any associated watches. > + */ > + if (inode->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE)) > + continue; > + > + need_iput_tmp = need_iput; > + need_iput = NULL; > + > + /* In case fsnotify_inode_delete() drops a reference. */ > + if (inode != need_iput_tmp) > + __iget(inode); > + else > + need_iput_tmp = NULL; > + > + /* In case the dropping of a reference would nuke next_i. */ > + if ((&next_i->i_sb_list != list) && > + atomic_read(&next_i->i_count) && > + !(next_i->i_state & (I_CLEAR | I_FREEING | I_WILL_FREE))) { > + __iget(next_i); > + need_iput = next_i; > + } > + > + /* > + * We can safely drop inode_lock here because we hold > + * references on both inode and next_i. Also no new inodes > + * will be added since the umount has begun. Finally, > + * iprune_mutex keeps shrink_icache_memory() away. > + */ > + spin_unlock(&inode_lock); > + > + if (need_iput_tmp) > + iput(need_iput_tmp);
iput(NULL) is legal.
> + /* for each watch, send FS_UNMOUNT and then remove it */ > + fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0); > + > + fsnotify_inode_delete(inode); > + > + iput(inode); > + > + spin_lock(&inode_lock); > + } > +} > +EXPORT_SYMBOL_GPL(fsnotify_unmount_inodes);
Why is it exported?
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