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Date: Mon, 24 Aug 2009 13:38:00 -0400
From: Eric Paris <eparis@...hat.com>
To: linux-kernel@...r.kernel.org, linux-fs-devel@...r.kernel.org
Cc: zdenek.kabelac@...il.com, torvalds@...ux-foundation.org,
christoph.thielecke@....de, akpm@...ux-foundation.org,
viro@...iv.linux.org.uk, grant.wilson@....co.uk,
mikko.cal@...il.com
Subject: [PATCH 1/3] 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@...hat.com>
---
fs/notify/inotify/inotify_user.c | 172 +++++++++++++++++++++++---------------
1 files changed, 103 insertions(+), 69 deletions(-)
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index dc32ed8..d8f73c2 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -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);
@@ -536,18 +485,103 @@ retry:
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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