inotify: seperate new watch creation updating existing watches
There is nothing known wrong with the inotify watch addition/modification but this patch seperates the two code paths to make them each easy to verify as correct. Signed-off-by: Eric Paris <eparis@redhat.com>
This commit is contained in:
Eric Paris
parent
1e23502cc5
commit
52cef7555a
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@ -431,80 +431,29 @@ static void inotify_free_mark(struct fsnotify_mark_entry *entry)
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kmem_cache_free(inotify_inode_mark_cachep, ientry);
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}
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static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
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static int inotify_update_existing_watch(struct fsnotify_group *group,
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struct inode *inode,
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u32 arg)
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{
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struct fsnotify_mark_entry *entry = NULL;
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struct fsnotify_mark_entry *entry;
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struct inotify_inode_mark_entry *ientry;
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struct inotify_inode_mark_entry *tmp_ientry;
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int ret = 0;
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int add = (arg & IN_MASK_ADD);
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__u32 mask;
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__u32 old_mask, new_mask;
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__u32 mask;
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int add = (arg & IN_MASK_ADD);
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int ret;
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/* don't allow invalid bits: we don't want flags set */
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mask = inotify_arg_to_mask(arg);
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if (unlikely(!mask))
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return -EINVAL;
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tmp_ientry = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
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if (unlikely(!tmp_ientry))
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return -ENOMEM;
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/* we set the mask at the end after attaching it */
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fsnotify_init_mark(&tmp_ientry->fsn_entry, inotify_free_mark);
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tmp_ientry->wd = -1;
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find_entry:
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spin_lock(&inode->i_lock);
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entry = fsnotify_find_mark_entry(group, inode);
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spin_unlock(&inode->i_lock);
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if (entry) {
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ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
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} else {
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ret = -ENOSPC;
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if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
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goto out_err;
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retry:
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ret = -ENOMEM;
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if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL)))
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goto out_err;
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if (!entry)
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return -ENOENT;
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spin_lock(&group->inotify_data.idr_lock);
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ret = idr_get_new_above(&group->inotify_data.idr, &tmp_ientry->fsn_entry,
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group->inotify_data.last_wd,
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&tmp_ientry->wd);
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spin_unlock(&group->inotify_data.idr_lock);
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if (ret) {
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if (ret == -EAGAIN)
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goto retry;
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goto out_err;
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}
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ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode);
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if (ret) {
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inotify_remove_from_idr(group, tmp_ientry);
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if (ret == -EEXIST)
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goto find_entry;
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goto out_err;
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}
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/* tmp_ientry has been added to the inode, so we are all set up.
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* now we just need to make sure tmp_ientry doesn't get freed and
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* we need to set up entry and ientry so the generic code can
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* do its thing. */
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ientry = tmp_ientry;
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entry = &ientry->fsn_entry;
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tmp_ientry = NULL;
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atomic_inc(&group->inotify_data.user->inotify_watches);
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/* update the idr hint */
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group->inotify_data.last_wd = ientry->wd;
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/* we put the mark on the idr, take a reference */
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fsnotify_get_mark(entry);
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}
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ret = ientry->wd;
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ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
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spin_lock(&entry->lock);
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@ -536,19 +485,104 @@ retry:
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fsnotify_recalc_group_mask(group);
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}
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/* this either matches fsnotify_find_mark_entry, or init_mark_entry
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* depending on which path we took... */
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/* return the wd */
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ret = ientry->wd;
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/* match the get from fsnotify_find_mark_entry() */
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fsnotify_put_mark(entry);
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out_err:
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/* could be an error, could be that we found an existing mark */
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if (tmp_ientry) {
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/* on the idr but didn't make it on the inode */
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if (tmp_ientry->wd != -1)
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inotify_remove_from_idr(group, tmp_ientry);
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kmem_cache_free(inotify_inode_mark_cachep, tmp_ientry);
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return ret;
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}
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static int inotify_new_watch(struct fsnotify_group *group,
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struct inode *inode,
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u32 arg)
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{
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struct inotify_inode_mark_entry *tmp_ientry;
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__u32 mask;
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int ret;
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/* don't allow invalid bits: we don't want flags set */
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mask = inotify_arg_to_mask(arg);
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if (unlikely(!mask))
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return -EINVAL;
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tmp_ientry = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
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if (unlikely(!tmp_ientry))
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return -ENOMEM;
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fsnotify_init_mark(&tmp_ientry->fsn_entry, inotify_free_mark);
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tmp_ientry->fsn_entry.mask = mask;
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tmp_ientry->wd = -1;
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ret = -ENOSPC;
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if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
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goto out_err;
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retry:
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ret = -ENOMEM;
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if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL)))
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goto out_err;
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spin_lock(&group->inotify_data.idr_lock);
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ret = idr_get_new_above(&group->inotify_data.idr, &tmp_ientry->fsn_entry,
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group->inotify_data.last_wd,
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&tmp_ientry->wd);
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spin_unlock(&group->inotify_data.idr_lock);
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if (ret) {
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/* idr was out of memory allocate and try again */
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if (ret == -EAGAIN)
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goto retry;
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goto out_err;
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}
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/* we are on the idr, now get on the inode */
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ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode);
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if (ret) {
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/* we failed to get on the inode, get off the idr */
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inotify_remove_from_idr(group, tmp_ientry);
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goto out_err;
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}
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/* we put the mark on the idr, take a reference */
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fsnotify_get_mark(&tmp_ientry->fsn_entry);
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/* update the idr hint, who cares about races, it's just a hint */
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group->inotify_data.last_wd = tmp_ientry->wd;
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/* increment the number of watches the user has */
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atomic_inc(&group->inotify_data.user->inotify_watches);
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/* return the watch descriptor for this new entry */
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ret = tmp_ientry->wd;
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/* match the ref from fsnotify_init_markentry() */
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fsnotify_put_mark(&tmp_ientry->fsn_entry);
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out_err:
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if (ret < 0)
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kmem_cache_free(inotify_inode_mark_cachep, tmp_ientry);
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return ret;
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}
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static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
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{
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int ret = 0;
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retry:
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/* try to update and existing watch with the new arg */
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ret = inotify_update_existing_watch(group, inode, arg);
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/* no mark present, try to add a new one */
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if (ret == -ENOENT)
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ret = inotify_new_watch(group, inode, arg);
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/*
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* inotify_new_watch could race with another thread which did an
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* inotify_new_watch between the update_existing and the add watch
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* here, go back and try to update an existing mark again.
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*/
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if (ret == -EEXIST)
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goto retry;
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return ret;
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}
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