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Message-ID: <6601abe90909171455g597fe672g1ca6d426e609f937@mail.gmail.com>
Date: Thu, 17 Sep 2009 14:55:43 -0700
From: Curt Wohlgemuth <curtw@...gle.com>
To: ext4 development <linux-ext4@...r.kernel.org>
Subject: [PATCH 2/2] ext4: Handle nested ext4_journal_start/stop calls without
a journal
This patch fixes a problem with handling nested calls to
ext4_journal_start/ext4_journal_stop, when there is no journal present.
Signed-off-by: Curt Wohlgemuth <curtw@...gle.com>
---
Instead of using the special value of
(handle_t *)0x1
to represent a handle when there is no journal present, we now use a real
handle_t, so we can use its ref counting. The h_transaction field now
determines if there is a journal present or not.
Note that ext4_handle_valid() previously returned 1 if a NULL handle was
sent in -- which is a bad use of this routine. Instead now, we'll get a
NULL pointer dereference...
diff -uprN orig/fs/ext4/ext4_jbd2.h new/fs/ext4/ext4_jbd2.h
--- orig/fs/ext4/ext4_jbd2.h 2009-09-17 14:32:13.000000000 -0700
+++ new/fs/ext4/ext4_jbd2.h 2009-09-17 14:31:01.000000000 -0700
@@ -161,11 +161,11 @@ int __ext4_handle_dirty_metadata(const c
handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks);
int __ext4_journal_stop(const char *where, handle_t *handle);
-#define EXT4_NOJOURNAL_HANDLE ((handle_t *) 0x1)
+#define EXT4_NOJOURNAL_TRANSACTION ((transaction_t *) 0x1)
static inline int ext4_handle_valid(handle_t *handle)
{
-- if (handle == EXT4_NOJOURNAL_HANDLE)
+ if (handle->h_transaction == EXT4_NOJOURNAL_TRANSACTION)
return 0;
return 1;
}
diff -uprN orig/fs/ext4/inode.c new/fs/ext4/inode.c
--- orig/fs/ext4/inode.c 2009-09-17 14:14:43.000000000 -0700
+++ new/fs/ext4/inode.c 2009-09-17 14:32:58.000000000 -0700
@@ -4931,12 +4931,14 @@ int ext4_write_inode(struct inode *inode
err = ext4_force_commit(inode->i_sb);
} else {
struct ext4_iloc iloc;
+ handle_t *handle = ext4_journal_start(inode, 1);
err = ext4_get_inode_loc(inode, &iloc);
if (err)
return err;
- err = ext4_do_update_inode(EXT4_NOJOURNAL_HANDLE,
- inode, &iloc, wait);
+ err = ext4_do_update_inode(handle, inode, &iloc, wait);
+
+ ext4_journal_stop(handle);
}
return err;
}
diff -uprN orig/fs/ext4/namei.c new/fs/ext4/namei.c
--- orig/fs/ext4/namei.c 2009-09-17 14:29:57.000000000 -0700
+++ new/fs/ext4/namei.c 2009-09-17 14:33:06.000000000 -0700
@@ -2076,7 +2076,8 @@ int ext4_orphan_del(handle_t *handle, st
struct ext4_iloc iloc;
int err = 0;
- if (!ext4_handle_valid(handle))
+ /* ext4_handle_valid() assumes a valid handle_t pointer */
+ if (handle && !ext4_handle_valid(handle))
return 0;
mutex_lock(&EXT4_SB(inode->i_sb)->s_orphan_lock);
diff -uprN orig/fs/ext4/super.c new/fs/ext4/super.c
--- orig/fs/ext4/super.c 2009-09-17 14:30:02.000000000 -0700
+++ new/fs/ext4/super.c 2009-09-17 14:33:06.000000000 -0700
@@ -198,6 +198,43 @@ void ext4_itable_unused_set(struct super
bg->bg_itable_unused_hi = cpu_to_le16(count >> 16);
}
+
+/* If the current tasks journal_info is NULL, create a new one, else
+ * bump its ref count */
+static handle_t *ext4_get_nojournal(void)
+{
+ handle_t *handle = current->journal_info;
+
+ if (handle) {
+ BUG_ON(handle->h_transaction != EXT4_NOJOURNAL_TRANSACTION);
+ handle->h_ref++;
+ return handle;
+ }
+
+ handle = jbd2_alloc_handle(GFP_NOFS);
+ if (!handle)
+ return NULL;
+
+ memset(handle, 0, sizeof(*handle));
+ handle->h_ref = 1;
+ handle->h_transaction = EXT4_NOJOURNAL_TRANSACTION;
+
+ current->journal_info = handle;
+ return handle;
+}
+
+
+/* Decrement the ref count, delete if now 0. */
+static void ext4_put_nojournal(handle_t *handle)
+{
+ BUG_ON(handle->h_transaction != EXT4_NOJOURNAL_TRANSACTION);
+ if (--handle->h_ref > 0)
+ return;
+
+ jbd2_free_handle(handle);
+ current->journal_info = NULL;
+}
+
/*
* Wrappers for jbd2_journal_start/end.
*
@@ -224,11 +261,7 @@ handle_t *ext4_journal_start_sb(struct s
}
return jbd2_journal_start(journal, nblocks);
}
- /*
- * We're not journaling, return the appropriate indication.
- */
- current->journal_info = EXT4_NOJOURNAL_HANDLE;
- return current->journal_info;
+ return ext4_get_nojournal();
}
/*
@@ -244,11 +277,7 @@ int __ext4_journal_stop(const char *wher
int rc;
if (!ext4_handle_valid(handle)) {
- /*
- * Do this here since we don't call jbd2_journal_stop() in
- * no-journal mode.
- */
- current->journal_info = NULL;
+ ext4_put_nojournal(handle);
return 0;
}
sb = handle->h_transaction->t_journal->j_private;
--
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