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From: Chris Mason <mason@suse.com>
To: linux-kernel@vger.kernel.org
Subject: [PATCH] LVM snapshot support for reiserfs and others
Date: Thu, 09 Aug 2001 14:35:21 -0400
Cc: torvalds@transmeta.com, viro@math.psu.edu, mge@sistina.com
Hello everyone,
This patch has been floating around for a while and is heavily used;
Heinz and I coded it last October or so. Minor change in the port to
2.4.8-pre was moving the sync_supers call in fsync_dev_lockfs to match
the changes in fsync_dev.
It adds calls to make use of the write_super_lockfs and unlockfs
callbacks, which allows the filesystem to do a full sync and block
new writers while LVM creates a snapshot. This way, the snapshot is actually
consistent on creation.
There's one reiserfs hunk in there (also very old) to fix a
bug in my initial reiserfs_write_super_lockfs call.
Patch against 2.4.8-pre6, it won't apply on top of -ac due to
Al's changes. I'm merging a bunch of stuff into -ac again,
I'll merge this as well.
Linus, please apply
-chris
diff -Nru a/drivers/md/lvm.c b/drivers/md/lvm.c
--- a/drivers/md/lvm.c Thu Aug 9 14:28:30 2001
+++ b/drivers/md/lvm.c Thu Aug 9 14:28:30 2001
@@ -162,7 +162,7 @@
#define DEVICE_OFF(device)
/* lvm_do_lv_create calls fsync_dev_lockfs()/unlockfs() */
-/* #define LVM_VFS_ENHANCEMENT */
+#define LVM_VFS_ENHANCEMENT
#include <linux/config.h>
#include <linux/version.h>
diff -Nru a/fs/buffer.c b/fs/buffer.c
--- a/fs/buffer.c Thu Aug 9 14:28:30 2001
+++ b/fs/buffer.c Thu Aug 9 14:28:30 2001
@@ -367,6 +367,33 @@
fsync_dev(dev);
}
+int fsync_dev_lockfs(kdev_t dev)
+{
+ sync_buffers(dev, 0);
+
+ lock_kernel();
+ /* note, the FS might need to start transactions to
+ ** sync the inodes, or the quota, no locking until
+ ** after these are done
+ */
+ sync_inodes(dev);
+ DQUOT_SYNC(dev);
+ /* if inodes or quotas could be dirtied during the
+ ** sync_supers_lockfs call, the FS is responsible for getting
+ ** them on disk, without deadlocking against the lock
+ **
+ ** we call sync_supers first so that
+ ** fsync_dev_lockfs == fsync_dev for filesystems that don't provide
+ ** a lockfs call. Yes, it could be done in sync_supers_lockfs
+ ** instead, but this just makes it more explicit...
+ */
+ sync_supers(dev) ;
+ sync_supers_lockfs(dev) ;
+ unlock_kernel();
+
+ return sync_buffers(dev, 1) ;
+}
+
asmlinkage long sys_sync(void)
{
fsync_dev(0);
diff -Nru a/fs/reiserfs/super.c b/fs/reiserfs/super.c
--- a/fs/reiserfs/super.c Thu Aug 9 14:28:30 2001
+++ b/fs/reiserfs/super.c Thu Aug 9 14:28:30 2001
@@ -80,7 +80,7 @@
reiserfs_prepare_for_journal(s, SB_BUFFER_WITH_SB(s), 1);
journal_mark_dirty(&th, s, SB_BUFFER_WITH_SB (s));
reiserfs_block_writes(&th) ;
- journal_end(&th, s, 1) ;
+ journal_end_sync(&th, s, 1) ;
}
s->s_dirt = dirty;
unlock_kernel() ;
diff -Nru a/fs/super.c b/fs/super.c
--- a/fs/super.c Thu Aug 9 14:28:30 2001
+++ b/fs/super.c Thu Aug 9 14:28:30 2001
@@ -672,6 +672,46 @@
}
}
+/*
+ * Note: don't check the dirty flag before waiting, we want the lock
+ * to happen every time this is called.
+ */
+void sync_supers_lockfs(kdev_t dev)
+{
+ struct super_block * sb;
+
+ for (sb = sb_entry(super_blocks.next);
+ sb != sb_entry(&super_blocks);
+ sb = sb_entry(sb->s_list.next)) {
+ if (!sb->s_dev)
+ continue;
+ if (dev && sb->s_dev != dev)
+ continue;
+ lock_super(sb);
+ if (sb->s_dev && (!dev || dev == sb->s_dev))
+ if (sb->s_op && sb->s_op->write_super_lockfs)
+ sb->s_op->write_super_lockfs(sb);
+ unlock_super(sb);
+ }
+}
+
+void unlockfs(kdev_t dev)
+{
+ struct super_block * sb;
+
+ for (sb = sb_entry(super_blocks.next);
+ sb != sb_entry(&super_blocks);
+ sb = sb_entry(sb->s_list.next)) {
+ if (!sb->s_dev)
+ continue;
+ if (dev && sb->s_dev != dev)
+ continue;
+ if (sb->s_dev && (!dev || dev == sb->s_dev))
+ if (sb->s_op && sb->s_op->unlockfs)
+ sb->s_op->unlockfs(sb);
+ }
+}
+
/**
* get_super - get the superblock of a device
* @dev: device to get the superblock for
diff -Nru a/include/linux/fs.h b/include/linux/fs.h
--- a/include/linux/fs.h Thu Aug 9 14:28:30 2001
+++ b/include/linux/fs.h Thu Aug 9 14:28:30 2001
@@ -1160,6 +1160,7 @@
extern void write_inode_now(struct inode *, int);
extern void sync_dev(kdev_t);
extern int fsync_dev(kdev_t);
+extern int fsync_dev_lockfs(kdev_t);
extern int fsync_super(struct super_block *);
extern void sync_inodes_sb(struct super_block *);
extern int fsync_inode_buffers(struct inode *);
@@ -1168,6 +1169,8 @@
extern void filemap_fdatasync(struct address_space *);
extern void filemap_fdatawait(struct address_space *);
extern void sync_supers(kdev_t);
+extern void sync_supers_lockfs(kdev_t);
+extern void unlockfs(kdev_t);
extern int bmap(struct inode *, int);
extern int notify_change(struct dentry *, struct iattr *);
extern int permission(struct inode *, int);
diff -Nru a/kernel/ksyms.c b/kernel/ksyms.c
--- a/kernel/ksyms.c Thu Aug 9 14:28:30 2001
+++ b/kernel/ksyms.c Thu Aug 9 14:28:30 2001
@@ -176,6 +176,8 @@
EXPORT_SYMBOL(invalidate_inode_pages);
EXPORT_SYMBOL(truncate_inode_pages);
EXPORT_SYMBOL(fsync_dev);
+EXPORT_SYMBOL(fsync_dev_lockfs);
+EXPORT_SYMBOL(unlockfs);
EXPORT_SYMBOL(permission);
EXPORT_SYMBOL(vfs_permission);
EXPORT_SYMBOL(inode_setattr);
-
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