From: Al Viro <viro@zeniv.linux.org.uk>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCHSET] sorting out RCU-delayed stuff in ->destroy_inode()
Date: Tue, 30 Apr 2019 05:26:24 +0100 [thread overview]
Message-ID: <20190430042623.GJ23075@ZenIV.linux.org.uk> (raw)
In-Reply-To: <F01D238D-8A6C-4629-ABC5-4A8BAC25951F@dilger.ca>
On Mon, Apr 29, 2019 at 10:18:04PM -0600, Andreas Dilger wrote:
> >
> > void *i_private; /* fs or device private pointer */
> > + void (*free_inode)(struct inode *);
>
> It seems like a waste to increase the size of every struct inode just to access
> a static pointer. Is this the only place that ->free_inode() is called? Why
> not move the ->free_inode() pointer into inode->i_fop->free_inode() so that it
> is still directly accessible at this point.
i_op, surely? In any case, increasing sizeof(struct inode) is not a problem -
if anything, I'd turn ->i_fop into an anon union with that. As in,
diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
index 9d80f9e0855e..b8d3ddd8b8db 100644
--- a/Documentation/filesystems/porting
+++ b/Documentation/filesystems/porting
@@ -655,3 +655,11 @@ in your dentry operations instead.
* if ->free_inode() is non-NULL, it gets scheduled by call_rcu()
* combination of NULL ->destroy_inode and NULL ->free_inode is
treated as NULL/free_inode_nonrcu, to preserve the compatibility.
+
+ Note that the callback (be it via ->free_inode() or explicit call_rcu()
+ in ->destroy_inode()) is *NOT* ordered wrt superblock destruction;
+ as the matter of fact, the superblock and all associated structures
+ might be already gone. The filesystem driver is guaranteed to be still
+ there, but that's it. Freeing memory in the callback is fine; doing
+ more than that is possible, but requires a lot of care and is best
+ avoided.
diff --git a/fs/inode.c b/fs/inode.c
index fb45590d284e..627e1766503a 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -211,8 +211,8 @@ EXPORT_SYMBOL(free_inode_nonrcu);
static void i_callback(struct rcu_head *head)
{
struct inode *inode = container_of(head, struct inode, i_rcu);
- if (inode->i_sb->s_op->free_inode)
- inode->i_sb->s_op->free_inode(inode);
+ if (inode->free_inode)
+ inode->free_inode(inode);
else
free_inode_nonrcu(inode);
}
@@ -236,6 +236,7 @@ static struct inode *alloc_inode(struct super_block *sb)
if (!ops->free_inode)
return NULL;
}
+ inode->free_inode = ops->free_inode;
i_callback(&inode->i_rcu);
return NULL;
}
@@ -276,6 +277,7 @@ static void destroy_inode(struct inode *inode)
if (!ops->free_inode)
return;
}
+ inode->free_inode = ops->free_inode;
call_rcu(&inode->i_rcu, i_callback);
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2e9b9f87caca..92732286b748 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -694,7 +694,10 @@ struct inode {
#ifdef CONFIG_IMA
atomic_t i_readcount; /* struct files open RO */
#endif
- const struct file_operations *i_fop; /* former ->i_op->default_file_ops */
+ union {
+ const struct file_operations *i_fop; /* former ->i_op->default_file_ops */
+ void (*free_inode)(struct inode *);
+ };
struct file_lock_context *i_flctx;
struct address_space i_data;
struct list_head i_devices;
next prev parent reply other threads:[~2019-04-30 4:26 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-16 17:49 [RFC][PATCHSET] sorting out RCU-delayed stuff in ->destroy_inode() Al Viro
2019-04-16 17:52 ` [RFC PATCH 01/62] securityfs: fix use-after-free on symlink traversal Al Viro
2019-04-16 17:52 ` [RFC PATCH 02/62] apparmorfs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 03/62] new inode method: ->free_inode() Al Viro
2019-04-16 17:52 ` [RFC PATCH 04/62] spufs: switch to ->free_inode() Al Viro
2019-04-16 17:52 ` [RFC PATCH 05/62] erofs: " Al Viro
2019-04-18 14:01 ` Gao Xiang
2019-04-16 17:52 ` [RFC PATCH 06/62] 9p: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 07/62] adfs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 08/62] affs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 09/62] befs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 10/62] bfs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 11/62] bdev: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 12/62] cifs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 13/62] debugfs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 14/62] efs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 15/62] ext2: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 16/62] f2fs: " Al Viro
2019-04-20 2:52 ` Chao Yu
2019-04-16 17:52 ` [RFC PATCH 17/62] fat: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 18/62] freevxfs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 19/62] gfs2: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 20/62] hfs: " Al Viro
2019-04-16 17:52 ` [RFC PATCH 21/62] hfsplus: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 22/62] hostfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 23/62] hpfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 24/62] isofs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 25/62] jffs2: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 26/62] minix: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 27/62] nfs{,4}: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 28/62] nilfs2: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 29/62] dlmfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 30/62] ocfs2: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 31/62] openpromfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 32/62] procfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 33/62] qnx4: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 34/62] qnx6: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 35/62] reiserfs: convert " Al Viro
2019-04-16 17:53 ` [RFC PATCH 36/62] romfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 37/62] squashfs: switch " Al Viro
2019-04-16 17:53 ` [RFC PATCH 38/62] ubifs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 39/62] udf: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 40/62] sysv: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 41/62] coda: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 42/62] ufs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 43/62] mqueue: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 44/62] bpf: " Al Viro
2019-04-16 18:07 ` Alexei Starovoitov
2019-04-16 21:34 ` Song Liu
2019-04-16 17:53 ` [RFC PATCH 45/62] rpcpipe: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 46/62] apparmor: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 47/62] securityfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 48/62] ntfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 49/62] dax: make use of ->free_inode() Al Viro
2019-04-18 12:16 ` Jan Kara
2019-04-18 16:58 ` Dan Williams
2019-04-16 17:53 ` [RFC PATCH 50/62] afs: switch to " Al Viro
2019-04-16 17:53 ` [RFC PATCH 51/62] btrfs: use ->free_inode() Al Viro
2019-04-16 17:53 ` [RFC PATCH 52/62] ceph: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 53/62] ecryptfs: make use of ->free_inode() Al Viro
2019-04-16 17:53 ` [RFC PATCH 54/62] ext4: " Al Viro
2019-04-18 12:10 ` Jan Kara
2019-04-16 17:53 ` [RFC PATCH 55/62] fuse: switch to ->free_inode() Al Viro
2019-04-16 17:53 ` [RFC PATCH 56/62] jfs: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 57/62] overlayfs: make use of ->free_inode() Al Viro
2019-04-16 17:53 ` [RFC PATCH 58/62] hugetlb: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 59/62] shmem: " Al Viro
2019-04-16 17:53 ` [RFC PATCH 60/62] orangefs: " Al Viro
2019-04-22 21:14 ` Mike Marshall
2019-04-22 21:56 ` Linus Torvalds
2019-04-22 23:10 ` Al Viro
2019-04-22 23:17 ` Mike Marshall
2019-04-16 17:53 ` [RFC PATCH 61/62] sockfs: switch to ->free_inode() Al Viro
2019-04-16 17:53 ` [RFC PATCH 62/62] coallocate socket->wq with socket itself Al Viro
2019-04-16 18:01 ` [RFC][PATCHSET] sorting out RCU-delayed stuff in ->destroy_inode() Linus Torvalds
2019-04-30 3:09 ` Al Viro
[not found] ` <CAHk-=wiMvCR0iENUVorfU-3EMC7G8RNSeHSQrz9tndP1uSg2BQ@mail.gmail.com>
2019-04-30 4:00 ` Al Viro
2019-05-01 1:59 ` Al Viro
2019-04-30 4:18 ` Andreas Dilger
2019-04-30 4:26 ` Al Viro [this message]
2019-04-30 5:26 ` Andreas Dilger
2019-04-17 15:55 ` David Sterba
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