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SubjectRe: mount hanging 2.4.12


[ bad lvm<->reiserfs locking patch causes hangs ]

Ok, here's an updated patch, one liner fix from the original.

-chris

Index: 0.41/fs/super.c
--- 0.41/fs/super.c Thu, 11 Oct 2001 09:27:57 -0400 root (linux/d/45_super.c 1.1.2.1.4.1.2.1 644)
+++ 0.42/fs/super.c Mon, 15 Oct 2001 03:42:49 -0400 root (linux/d/45_super.c 1.1.2.1.4.1.2.2 644)
@@ -54,6 +54,8 @@
LIST_HEAD(super_blocks);
spinlock_t sb_lock = SPIN_LOCK_UNLOCKED;

+static DECLARE_MUTEX(lockfs_sem);
+
/*
* Handling of filesystem drivers list.
* Rules:
@@ -322,6 +324,19 @@
sb->s_op->write_super(sb);
unlock_super(sb);
}
+
+static inline void write_super_lockfs(struct super_block *sb)
+{
+ lock_super(sb);
+ if (sb->s_root && sb->s_op) {
+ if (sb->s_dirt && sb->s_op->write_super)
+ sb->s_op->write_super(sb);
+ if (sb->s_op->write_super_lockfs) {
+ sb->s_op->write_super_lockfs(sb);
+ }
+ }
+ unlock_super(sb);
+}

/*
* Note: check the dirty flag before waiting, so we don't
@@ -357,6 +372,39 @@
spin_unlock(&sb_lock);
}

+/*
+ * Note: don't check the dirty flag before waiting, we want the lock
+ * to happen every time this is called. dev must be non-zero
+ */
+void sync_supers_lockfs(kdev_t dev)
+{
+ struct super_block * sb;
+
+ down(&lockfs_sem);
+ if (dev) {
+ sb = get_super(dev);
+ if (sb) {
+ write_super_lockfs(sb);
+ drop_super(sb);
+ }
+ }
+}
+
+void unlockfs(kdev_t dev)
+{
+ struct super_block * sb;
+
+ if (dev) {
+ sb = get_super(dev);
+ if (sb) {
+ if (sb->s_op && sb->s_op->unlockfs)
+ sb->s_op->unlockfs(sb) ;
+ drop_super(sb);
+ }
+ }
+ up(&lockfs_sem);
+}
+
/**
* get_super - get the superblock of a device
* @dev: device to get the superblock for
@@ -578,6 +626,7 @@
if (!s)
goto out1;
down_write(&s->s_umount);
+ down(&lockfs_sem) ;

error = -EBUSY;
restart:
@@ -590,11 +639,13 @@
if (old->s_type != fs_type ||
((flags ^ old->s_flags) & MS_RDONLY)) {
spin_unlock(&sb_lock);
+ up(&lockfs_sem);
put_super(s);
goto out1;
}
if (!grab_super(old))
goto restart;
+ up(&lockfs_sem);
put_super(s);
blkdev_put(bdev, BDEV_FS);
path_release(&nd);
@@ -615,6 +666,9 @@
if (!fs_type->read_super(s, data, flags & MS_VERBOSE ? 1 : 0))
goto out_fail;
unlock_super(s);
+
+ up(&lockfs_sem);
+
get_filesystem(fs_type);
path_release(&nd);
return s;
@@ -623,6 +677,7 @@
s->s_dev = 0;
s->s_bdev = 0;
s->s_type = NULL;
+ up(&lockfs_sem) ;
unlock_super(s);
spin_lock(&sb_lock);
list_del(&s->s_list);
@@ -728,6 +783,7 @@
sb->s_count -= S_BIAS;
spin_unlock(&sb_lock);

+ down(&lockfs_sem);
down_write(&sb->s_umount);
lock_kernel();
sb->s_root = NULL;
@@ -744,6 +800,7 @@
if (sop->put_super)
sop->put_super(sb);
}
+ up(&lockfs_sem);

/* Forget any remaining inodes */
if (invalidate_inodes(sb)) {
Index: 0.41/fs/buffer.c
--- 0.41/fs/buffer.c Sun, 14 Oct 2001 10:34:39 -0400 root (linux/i/46_buffer.c 1.1.2.1.9.1.4.1 644)
+++ 0.42/fs/buffer.c Mon, 15 Oct 2001 03:42:49 -0400 root (linux/i/46_buffer.c 1.1.2.1.9.1.4.2 644)
@@ -359,6 +359,34 @@
fsync_dev(dev);
}

+int fsync_dev_lockfs(kdev_t dev)
+{
+ /* you are not allowed to try locking all the filesystems
+ ** on the system, your chances of getting through without
+ ** total deadlock are slim to none.
+ */
+ if (!dev)
+ return fsync_dev(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
+ */
+ sync_supers_lockfs(dev) ;
+ unlock_kernel();
+
+ return sync_buffers(dev, 1) ;
+}
+
asmlinkage long sys_sync(void)
{
fsync_dev(0);
Index: 0.41/drivers/md/lvm.c
--- 0.41/drivers/md/lvm.c Sun, 23 Sep 2001 20:11:16 -0400 root (linux/i/c/30_lvm.c 1.1.2.1 644)
+++ 0.42/drivers/md/lvm.c Mon, 15 Oct 2001 03:42:49 -0400 root (linux/i/c/30_lvm.c 1.1.2.1.9.1 644)
@@ -161,9 +161,6 @@
#define MAJOR_NR LVM_BLK_MAJOR
#define DEVICE_OFF(device)

-/* lvm_do_lv_create calls fsync_dev_lockfs()/unlockfs() */
-/* #define LVM_VFS_ENHANCEMENT */
-
#include <linux/config.h>
#include <linux/version.h>
#include <linux/module.h>
@@ -2301,12 +2298,8 @@
if (lv_ptr->lv_access & LV_SNAPSHOT) {
lv_t *org = lv_ptr->lv_snapshot_org, *last;

- /* sync the original logical volume */
- fsync_dev(org->lv_dev);
-#ifdef LVM_VFS_ENHANCEMENT
/* VFS function call to sync and lock the filesystem */
fsync_dev_lockfs(org->lv_dev);
-#endif

down(&org->lv_snapshot_sem);
org->lv_access |= LV_SNAPSHOT_ORG;
@@ -2326,12 +2319,10 @@
else
set_device_ro(lv_ptr->lv_dev, 1);

-#ifdef LVM_VFS_ENHANCEMENT
/* VFS function call to unlock the filesystem */
if (lv_ptr->lv_access & LV_SNAPSHOT) {
unlockfs(lv_ptr->lv_snapshot_org->lv_dev);
}
-#endif

lv_ptr->vg = vg_ptr;

Index: 0.41/kernel/ksyms.c
--- 0.41/kernel/ksyms.c Sun, 14 Oct 2001 10:34:39 -0400 root (linux/n/c/22_ksyms.c 1.1.2.1.9.1.4.1 644)
+++ 0.42/kernel/ksyms.c Mon, 15 Oct 2001 03:42:49 -0400 root (linux/n/c/22_ksyms.c 1.1.2.1.9.1.4.2 644)
@@ -178,6 +178,8 @@
EXPORT_SYMBOL(invalidate_inode_pages);
EXPORT_SYMBOL(truncate_inode_pages);
EXPORT_SYMBOL(fsync_dev);
+EXPORT_SYMBOL(fsync_dev_lockfs);
+EXPORT_SYMBOL(unlockfs);
EXPORT_SYMBOL(fsync_no_super);
EXPORT_SYMBOL(permission);
EXPORT_SYMBOL(vfs_permission);
Index: 0.41/include/linux/fs.h
--- 0.41/include/linux/fs.h Sun, 14 Oct 2001 10:34:39 -0400 root (linux/f/d/9_fs.h 1.1.2.1.10.1.2.2 644)
+++ 0.42/include/linux/fs.h Mon, 15 Oct 2001 03:42:49 -0400 root (linux/f/d/9_fs.h 1.1.2.1.10.1.2.2.1.1 644)
@@ -1185,6 +1185,7 @@
extern int sync_buffers(kdev_t, 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 int fsync_no_super(kdev_t);
extern void sync_inodes_sb(struct super_block *);
@@ -1196,6 +1197,8 @@
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);
-
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