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inotify: seperate new watch creation updating existing watches
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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>
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Eric Paris committed Aug 27, 2009
1 parent 1e23502 commit 52cef75
Showing 1 changed file with 103 additions and 69 deletions.
172 changes: 103 additions & 69 deletions fs/notify/inotify/inotify_user.c
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Original file line number Diff line number Diff line change
Expand Up @@ -431,80 +431,29 @@ static void inotify_free_mark(struct fsnotify_mark_entry *entry)
kmem_cache_free(inotify_inode_mark_cachep, ientry);
}

static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
static int inotify_update_existing_watch(struct fsnotify_group *group,
struct inode *inode,
u32 arg)
{
struct fsnotify_mark_entry *entry = NULL;
struct fsnotify_mark_entry *entry;
struct inotify_inode_mark_entry *ientry;
struct inotify_inode_mark_entry *tmp_ientry;
int ret = 0;
int add = (arg & IN_MASK_ADD);
__u32 mask;
__u32 old_mask, new_mask;
__u32 mask;
int add = (arg & IN_MASK_ADD);
int ret;

/* don't allow invalid bits: we don't want flags set */
mask = inotify_arg_to_mask(arg);
if (unlikely(!mask))
return -EINVAL;

tmp_ientry = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
if (unlikely(!tmp_ientry))
return -ENOMEM;
/* we set the mask at the end after attaching it */
fsnotify_init_mark(&tmp_ientry->fsn_entry, inotify_free_mark);
tmp_ientry->wd = -1;

find_entry:
spin_lock(&inode->i_lock);
entry = fsnotify_find_mark_entry(group, inode);
spin_unlock(&inode->i_lock);
if (entry) {
ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);
} else {
ret = -ENOSPC;
if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
goto out_err;
retry:
ret = -ENOMEM;
if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL)))
goto out_err;

spin_lock(&group->inotify_data.idr_lock);
ret = idr_get_new_above(&group->inotify_data.idr, &tmp_ientry->fsn_entry,
group->inotify_data.last_wd,
&tmp_ientry->wd);
spin_unlock(&group->inotify_data.idr_lock);
if (ret) {
if (ret == -EAGAIN)
goto retry;
goto out_err;
}
if (!entry)
return -ENOENT;

ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode);
if (ret) {
inotify_remove_from_idr(group, tmp_ientry);
if (ret == -EEXIST)
goto find_entry;
goto out_err;
}

/* tmp_ientry has been added to the inode, so we are all set up.
* now we just need to make sure tmp_ientry doesn't get freed and
* we need to set up entry and ientry so the generic code can
* do its thing. */
ientry = tmp_ientry;
entry = &ientry->fsn_entry;
tmp_ientry = NULL;

atomic_inc(&group->inotify_data.user->inotify_watches);

/* update the idr hint */
group->inotify_data.last_wd = ientry->wd;

/* we put the mark on the idr, take a reference */
fsnotify_get_mark(entry);
}

ret = ientry->wd;
ientry = container_of(entry, struct inotify_inode_mark_entry, fsn_entry);

spin_lock(&entry->lock);

Expand Down Expand Up @@ -536,18 +485,103 @@ static int inotify_update_watch(struct fsnotify_group *group, struct inode *inod
fsnotify_recalc_group_mask(group);
}

/* this either matches fsnotify_find_mark_entry, or init_mark_entry
* depending on which path we took... */
/* return the wd */
ret = ientry->wd;

/* match the get from fsnotify_find_mark_entry() */
fsnotify_put_mark(entry);

return ret;
}

static int inotify_new_watch(struct fsnotify_group *group,
struct inode *inode,
u32 arg)
{
struct inotify_inode_mark_entry *tmp_ientry;
__u32 mask;
int ret;

/* don't allow invalid bits: we don't want flags set */
mask = inotify_arg_to_mask(arg);
if (unlikely(!mask))
return -EINVAL;

tmp_ientry = kmem_cache_alloc(inotify_inode_mark_cachep, GFP_KERNEL);
if (unlikely(!tmp_ientry))
return -ENOMEM;

fsnotify_init_mark(&tmp_ientry->fsn_entry, inotify_free_mark);
tmp_ientry->fsn_entry.mask = mask;
tmp_ientry->wd = -1;

ret = -ENOSPC;
if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
goto out_err;
retry:
ret = -ENOMEM;
if (unlikely(!idr_pre_get(&group->inotify_data.idr, GFP_KERNEL)))
goto out_err;

spin_lock(&group->inotify_data.idr_lock);
ret = idr_get_new_above(&group->inotify_data.idr, &tmp_ientry->fsn_entry,
group->inotify_data.last_wd,
&tmp_ientry->wd);
spin_unlock(&group->inotify_data.idr_lock);
if (ret) {
/* idr was out of memory allocate and try again */
if (ret == -EAGAIN)
goto retry;
goto out_err;
}

/* we are on the idr, now get on the inode */
ret = fsnotify_add_mark(&tmp_ientry->fsn_entry, group, inode);
if (ret) {
/* we failed to get on the inode, get off the idr */
inotify_remove_from_idr(group, tmp_ientry);
goto out_err;
}

/* we put the mark on the idr, take a reference */
fsnotify_get_mark(&tmp_ientry->fsn_entry);

/* update the idr hint, who cares about races, it's just a hint */
group->inotify_data.last_wd = tmp_ientry->wd;

/* increment the number of watches the user has */
atomic_inc(&group->inotify_data.user->inotify_watches);

/* return the watch descriptor for this new entry */
ret = tmp_ientry->wd;

/* match the ref from fsnotify_init_markentry() */
fsnotify_put_mark(&tmp_ientry->fsn_entry);

out_err:
/* could be an error, could be that we found an existing mark */
if (tmp_ientry) {
/* on the idr but didn't make it on the inode */
if (tmp_ientry->wd != -1)
inotify_remove_from_idr(group, tmp_ientry);
if (ret < 0)
kmem_cache_free(inotify_inode_mark_cachep, tmp_ientry);
}

return ret;
}

static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
{
int ret = 0;

retry:
/* try to update and existing watch with the new arg */
ret = inotify_update_existing_watch(group, inode, arg);
/* no mark present, try to add a new one */
if (ret == -ENOENT)
ret = inotify_new_watch(group, inode, arg);
/*
* inotify_new_watch could race with another thread which did an
* inotify_new_watch between the update_existing and the add watch
* here, go back and try to update an existing mark again.
*/
if (ret == -EEXIST)
goto retry;

return ret;
}
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