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Date: Tue, 21 Aug 2012 17:40:04 +0400
From: Cyrill Gorcunov <gorcunov@...nvz.org>
To: "J. Bruce Fields" <bfields@...ldses.org>
Cc: Pavel Emelyanov <xemul@...allels.com>,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
Al Viro <viro@...iv.linux.org.uk>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
Alexey Dobriyan <adobriyan@...il.com>,
Andrew Morton <akpm@...ux-foundation.org>,
James Bottomley <jbottomley@...allels.com>,
Matthew Helsley <matt.helsley@...il.com>
Subject: Re: [patch 4/8] fs, exportfs: Add export_encode_inode_fh helper
On Tue, Aug 21, 2012 at 08:29:08AM -0400, J. Bruce Fields wrote:
> > Initial problem -- we don't know what is being watched by an inotify fd.
> >
> > Having a dentry somewhere was the 1st attempt to solve this -- keep a path
> > in inotify and show it when required. It doesn't work since holding a ref on
> > path changes the behavior of watched inode (we cannot rename/unlink/remount
> > it the same way as we could before patching the kernel).
>
> OK. So if you don't mind the fact that there are filesystems with
> inotify support but not filehandle support, then I think generating a
> filehandle early as you describe would work. I guess it's a little more
> memory per watched inode.
So, I thought about something like below, any comments?
---
fs/notify/inotify/inotify.h | 8 +++++++
fs/notify/inotify/inotify_user.c | 41 ++++++++++++++++++++++++++++++++++-----
2 files changed, 44 insertions(+), 5 deletions(-)
Index: linux-2.6.git/fs/notify/inotify/inotify.h
===================================================================
--- linux-2.6.git.orig/fs/notify/inotify/inotify.h
+++ linux-2.6.git/fs/notify/inotify/inotify.h
@@ -1,6 +1,7 @@
#include <linux/fsnotify_backend.h>
#include <linux/inotify.h>
#include <linux/slab.h> /* struct kmem_cache */
+#include <linux/exportfs.h>
extern struct kmem_cache *event_priv_cachep;
@@ -9,9 +10,16 @@ struct inotify_event_private_data {
int wd;
};
+#if defined(CONFIG_PROC_FS) && defined(CONFIG_EXPORTFS) && defined(CONFIG_CHECKPOINT_RESTORE)
+# define INOTIFY_USE_FHANDLE
+#endif
+
struct inotify_inode_mark {
struct fsnotify_mark fsn_mark;
int wd;
+#ifdef INOTIFY_USE_FHANDLE
+ __u8 fhandle[sizeof(struct file_handle) + MAX_HANDLE_SZ];
+#endif
};
extern void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark,
Index: linux-2.6.git/fs/notify/inotify/inotify_user.c
===================================================================
--- linux-2.6.git.orig/fs/notify/inotify/inotify_user.c
+++ linux-2.6.git/fs/notify/inotify/inotify_user.c
@@ -566,6 +566,32 @@ static void inotify_free_mark(struct fsn
kmem_cache_free(inotify_inode_mark_cachep, i_mark);
}
+#ifdef INOTIFY_USE_FHANDLE
+static int inotify_encode_wd_fhandle(struct inotify_inode_mark *mark, struct dentry *dentry)
+{
+ struct file_handle *fhandle = (struct file_handle *)mark->fhandle;
+ int size, ret;
+
+ BUILD_BUG_ON(sizeof(mark->fhandle) <= sizeof(struct file_handle));
+
+ fhandle->handle_bytes = sizeof(mark->fhandle) - sizeof(struct file_handle);
+ size = fhandle->handle_bytes >> 2;
+
+ ret = exportfs_encode_fh(dentry, (struct fid *)fhandle->f_handle, &size, 0);
+ if ((ret == 255) || (ret == -ENOSPC))
+ return -EOVERFLOW;
+
+ fhandle->handle_type = ret;
+
+ return 0;
+}
+# else
+static int inotify_encode_wd_fhandle(struct inotify_inode_mark *mark, struct dentry *dentry)
+{
+ return 0;
+}
+#endif
+
static int inotify_update_existing_watch(struct fsnotify_group *group,
struct inode *inode,
u32 arg)
@@ -621,10 +647,11 @@ static int inotify_update_existing_watch
}
static int inotify_new_watch(struct fsnotify_group *group,
- struct inode *inode,
+ struct dentry *dentry,
u32 arg)
{
struct inotify_inode_mark *tmp_i_mark;
+ struct inode *inode = dentry->d_inode;
__u32 mask;
int ret;
struct idr *idr = &group->inotify_data.idr;
@@ -647,6 +674,10 @@ static int inotify_new_watch(struct fsno
if (atomic_read(&group->inotify_data.user->inotify_watches) >= inotify_max_user_watches)
goto out_err;
+ ret = inotify_encode_wd_fhandle(tmp_i_mark, dentry);
+ if (ret)
+ goto out_err;
+
ret = inotify_add_to_idr(idr, idr_lock, &group->inotify_data.last_wd,
tmp_i_mark);
if (ret)
@@ -673,16 +704,16 @@ out_err:
return ret;
}
-static int inotify_update_watch(struct fsnotify_group *group, struct inode *inode, u32 arg)
+static int inotify_update_watch(struct fsnotify_group *group, struct dentry *dentry, u32 arg)
{
int ret = 0;
retry:
/* try to update and existing watch with the new arg */
- ret = inotify_update_existing_watch(group, inode, arg);
+ ret = inotify_update_existing_watch(group, dentry->d_inode, arg);
/* no mark present, try to add a new one */
if (ret == -ENOENT)
- ret = inotify_new_watch(group, inode, arg);
+ ret = inotify_new_watch(group, dentry, arg);
/*
* inotify_new_watch could race with another thread which did an
* inotify_new_watch between the update_existing and the add watch
@@ -785,7 +816,7 @@ SYSCALL_DEFINE3(inotify_add_watch, int,
group = filp->private_data;
/* create/update an inode mark */
- ret = inotify_update_watch(group, inode, mask);
+ ret = inotify_update_watch(group, path.dentry, mask);
path_put(&path);
fput_and_out:
fput_light(filp, fput_needed);
--
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