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Date: Fri, 18 Sep 2009 14:33:04 -0700
From: Curt Wohlgemuth <curtw@...gle.com>
To: Andreas Dilger <adilger@....com>
Cc: ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2/2] ext4: Handle nested ext4_journal_start/stop calls
without a journal
Here's version 2, thanks to Andreas' suggestion.
Curt
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>
---
Taking Andreas' suggestion, what I'm calling "an allocated handle that
doesn't use a journal" is now identified by a value in the range
[1, 4095]
A handle with value 0 (NULL) still represents "an unallocated handle."
I added a comment atop ext4_handle_valid() to indicate that sending it a
NULL pointer was just wrong.
diff -uprN orig/fs/ext4/ext4_jbd2.h new/fs/ext4/ext4_jbd2.h
--- orig/fs/ext4/ext4_jbd2.h 2009-09-18 14:04:15.000000000 -0700
+++ new/fs/ext4/ext4_jbd2.h 2009-09-18 14:17:31.000000000 -0700
@@ -161,11 +161,13 @@ 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_MAX_REF_COUNT ((unsigned long) 4096)
+/* Note: Do not use this for NULL handles. This is only to determine if
+ * a properly allocated handle is using a journal or not. */
static inline int ext4_handle_valid(handle_t *handle)
{
- if (handle == EXT4_NOJOURNAL_HANDLE)
+ if ((unsigned long)handle < EXT4_NOJOURNAL_MAX_REF_COUNT)
return 0;
return 1;
}
diff -uprN orig/fs/ext4/inode.c new/fs/ext4/inode.c
--- orig/fs/ext4/inode.c 2009-09-18 14:04:15.000000000 -0700
+++ new/fs/ext4/inode.c 2009-09-18 14:17:31.000000000 -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 2009-09-18 14:04:15.000000000 -0700
+++ new/fs/ext4/namei.c 2009-09-18 14:17:31.000000000 -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 2009-09-18 14:04:15.000000000 -0700
+++ new/fs/ext4/super.c 2009-09-18 14:17:31.000000000 -0700
@@ -198,6 +198,36 @@ void ext4_itable_unused_set(struct super
bg->bg_itable_unused_hi = cpu_to_le16(count >> 16);
}
+
+/* Just increment the non-pointer handle value */
+static handle_t *ext4_get_nojournal(void)
+{
+ handle_t *handle = current->journal_info;
+ unsigned long ref_cnt = (unsigned long)handle;
+
+ BUG_ON(ref_cnt >= EXT4_NOJOURNAL_MAX_REF_COUNT);
+
+ ref_cnt++;
+ handle = (handle_t *)ref_cnt;
+
+ current->journal_info = handle;
+ return handle;
+}
+
+
+/* Decrement the non-pointer handle value */
+static void ext4_put_nojournal(handle_t *handle)
+{
+ unsigned long ref_cnt = (unsigned long)handle;
+
+ BUG_ON(ref_cnt == 0);
+
+ ref_cnt--;
+ handle = (handle_t *)ref_cnt;
+
+ current->journal_info = handle;
+}
+
/*
* Wrappers for jbd2_journal_start/end.
*
@@ -224,11 +254,7 @@ 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 +270,7 @@ 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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