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Message-Id: <1321873893-4544-4-git-send-email-miklos@szeredi.hu>
Date: Mon, 21 Nov 2011 12:11:32 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: viro@...IV.linux.org.uk
Cc: hch@...radead.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, jack@...e.cz,
akpm@...ux-foundation.org, toshi.okajima@...fujitsu.com,
mszeredi@...e.cz
Subject: [PATCH 3/4] vfs: count unlinked inodes
From: Miklos Szeredi <mszeredi@...e.cz>
Add a new counter to the superblock that keeps track of unlinked but
not yet deleted inodes.
Do not WARN_ON if set_nlink is called with zero count, just do a
ratelimited printk. This happens on xfs and probably other
filesystems after an unclean shutdown when the filesystem reads inodes
which already have zero i_nlink. Reported by Christoph Hellwig.
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@...fujitsu.com>
---
fs/inode.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/fs.h | 61 ++++---------------------------------
2 files changed, 92 insertions(+), 54 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index ee4e66b..5f8fd6b 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -26,6 +26,7 @@
#include <linux/ima.h>
#include <linux/cred.h>
#include <linux/buffer_head.h> /* for inode_has_buffers */
+#include <linux/ratelimit.h>
#include "internal.h"
/*
@@ -241,6 +242,11 @@ void __destroy_inode(struct inode *inode)
BUG_ON(inode_has_buffers(inode));
security_inode_free(inode);
fsnotify_inode_delete(inode);
+ if (!inode->i_nlink) {
+ WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
+ atomic_long_dec(&inode->i_sb->s_remove_count);
+ }
+
#ifdef CONFIG_FS_POSIX_ACL
if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
posix_acl_release(inode->i_acl);
@@ -268,6 +274,85 @@ static void destroy_inode(struct inode *inode)
call_rcu(&inode->i_rcu, i_callback);
}
+/**
+ * drop_nlink - directly drop an inode's link count
+ * @inode: inode
+ *
+ * This is a low-level filesystem helper to replace any
+ * direct filesystem manipulation of i_nlink. In cases
+ * where we are attempting to track writes to the
+ * filesystem, a decrement to zero means an imminent
+ * write when the file is truncated and actually unlinked
+ * on the filesystem.
+ */
+void drop_nlink(struct inode *inode)
+{
+ WARN_ON(inode->i_nlink == 0);
+ inode->__i_nlink--;
+ if (!inode->i_nlink)
+ atomic_long_inc(&inode->i_sb->s_remove_count);
+}
+EXPORT_SYMBOL(drop_nlink);
+
+/**
+ * clear_nlink - directly zero an inode's link count
+ * @inode: inode
+ *
+ * This is a low-level filesystem helper to replace any
+ * direct filesystem manipulation of i_nlink. See
+ * drop_nlink() for why we care about i_nlink hitting zero.
+ */
+void clear_nlink(struct inode *inode)
+{
+ if (inode->i_nlink) {
+ inode->__i_nlink = 0;
+ atomic_long_inc(&inode->i_sb->s_remove_count);
+ }
+}
+EXPORT_SYMBOL(clear_nlink);
+
+/**
+ * set_nlink - directly set an inode's link count
+ * @inode: inode
+ * @nlink: new nlink (should be non-zero)
+ *
+ * This is a low-level filesystem helper to replace any
+ * direct filesystem manipulation of i_nlink.
+ */
+void set_nlink(struct inode *inode, unsigned int nlink)
+{
+ if (!nlink) {
+ printk_ratelimited(KERN_INFO
+ "set_nlink() clearing i_nlink on %s inode %li\n",
+ inode->i_sb->s_type->name, inode->i_ino);
+ clear_nlink(inode);
+ } else {
+ /* Yes, some filesystems do change nlink from zero to one */
+ if (inode->i_nlink == 0)
+ atomic_long_dec(&inode->i_sb->s_remove_count);
+
+ inode->__i_nlink = nlink;
+ }
+}
+EXPORT_SYMBOL(set_nlink);
+
+/**
+ * inc_nlink - directly increment an inode's link count
+ * @inode: inode
+ *
+ * This is a low-level filesystem helper to replace any
+ * direct filesystem manipulation of i_nlink. Currently,
+ * it is only here for parity with dec_nlink().
+ */
+void inc_nlink(struct inode *inode)
+{
+ if (WARN_ON(inode->i_nlink == 0))
+ atomic_long_dec(&inode->i_sb->s_remove_count);
+
+ inode->__i_nlink++;
+}
+EXPORT_SYMBOL(inc_nlink);
+
void address_space_init_once(struct address_space *mapping)
{
memset(mapping, 0, sizeof(*mapping));
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 58f50f2..f4636c3 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1483,6 +1483,9 @@ struct super_block {
struct shrinker s_shrink; /* per-sb shrinker handle */
+ /* Number of inodes with nlink == 0 but still referenced */
+ atomic_long_t s_remove_count;
+
/* Being remounted read-only */
int s_readonly_remount;
};
@@ -1768,31 +1771,10 @@ static inline void mark_inode_dirty_sync(struct inode *inode)
__mark_inode_dirty(inode, I_DIRTY_SYNC);
}
-/**
- * set_nlink - directly set an inode's link count
- * @inode: inode
- * @nlink: new nlink (should be non-zero)
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink.
- */
-static inline void set_nlink(struct inode *inode, unsigned int nlink)
-{
- inode->__i_nlink = nlink;
-}
-
-/**
- * inc_nlink - directly increment an inode's link count
- * @inode: inode
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink. Currently,
- * it is only here for parity with dec_nlink().
- */
-static inline void inc_nlink(struct inode *inode)
-{
- inode->__i_nlink++;
-}
+extern void inc_nlink(struct inode *inode);
+extern void drop_nlink(struct inode *inode);
+extern void clear_nlink(struct inode *inode);
+extern void set_nlink(struct inode *inode, unsigned int nlink);
static inline void inode_inc_link_count(struct inode *inode)
{
@@ -1800,35 +1782,6 @@ static inline void inode_inc_link_count(struct inode *inode)
mark_inode_dirty(inode);
}
-/**
- * drop_nlink - directly drop an inode's link count
- * @inode: inode
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink. In cases
- * where we are attempting to track writes to the
- * filesystem, a decrement to zero means an imminent
- * write when the file is truncated and actually unlinked
- * on the filesystem.
- */
-static inline void drop_nlink(struct inode *inode)
-{
- inode->__i_nlink--;
-}
-
-/**
- * clear_nlink - directly zero an inode's link count
- * @inode: inode
- *
- * This is a low-level filesystem helper to replace any
- * direct filesystem manipulation of i_nlink. See
- * drop_nlink() for why we care about i_nlink hitting zero.
- */
-static inline void clear_nlink(struct inode *inode)
-{
- inode->__i_nlink = 0;
-}
-
static inline void inode_dec_link_count(struct inode *inode)
{
drop_nlink(inode);
--
1.7.7
--
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