We don't need mount_sem to be held for get_sb_*/do_kern_mount anymore.
The only thing it actually protects now is the mount tree.
Patch takes aforementioned functions (i.e. work with superblocks) out
of mount_sem. For one thing, that allows ->read_super() to do filp_open()
and its ilk if we want to do that - we don't have to be afraid of
automounter being triggered and deadlocked on mount_sem. Moreover, it
makes locking in fs/super.c simpler - mount_sem now has well-defined
object of protection (mount tree).
Patch had been in -ac for several weeks and got decent beating locally
(several months). No complaints so far. Please, apply (it's incremental
to do_kern_mount() one).
diff -urN S10-pre4-do_kern_mount/fs/super.c S10-pre4-mount_sem/fs/super.c
--- S10-pre4-do_kern_mount/fs/super.c Sun Sep 2 23:28:26 2001
+++ S10-pre4-mount_sem/fs/super.c Sun Sep 2 23:28:49 2001
@@ -923,7 +923,6 @@
bdops = devfs_get_ops ( devfs_get_handle_from_inode (inode) );
if (bdops) bdev->bd_op = bdops;
/* Done with lookups, semaphore down */
- down(&mount_sem);
dev = to_kdev_t(bdev->bd_dev);
if (!(flags & MS_RDONLY))
mode |= FMODE_WRITE;
@@ -998,7 +997,6 @@
blkdev_put(bdev, BDEV_FS);
out:
path_release(&nd);
- up(&mount_sem);
return ERR_PTR(error);
}
@@ -1007,7 +1005,6 @@
{
kdev_t dev;
int error = -EMFILE;
- down(&mount_sem);
dev = get_unnamed_dev();
if (dev) {
struct super_block * sb;
@@ -1019,7 +1016,6 @@
}
put_unnamed_dev(dev);
}
- up(&mount_sem);
return ERR_PTR(error);
}
@@ -1034,7 +1030,6 @@
* Get the superblock of kernel-wide instance, but
* keep the reference to fs_type.
*/
- down(&mount_sem);
retry:
spin_lock(&sb_lock);
if (!list_empty(&fs_type->fs_supers)) {
@@ -1050,7 +1045,6 @@
kdev_t dev = get_unnamed_dev();
if (!dev) {
put_super(s);
- up(&mount_sem);
return ERR_PTR(-EMFILE);
}
s->s_dev = dev;
@@ -1079,7 +1073,6 @@
spin_unlock(&sb_lock);
put_super(s);
put_unnamed_dev(dev);
- up(&mount_sem);
return ERR_PTR(-EINVAL);
}
}
@@ -1436,7 +1429,7 @@
strcpy(mnt->mnt_devname, name);
}
- /* get superblock, locks mount_sem on success */
+ /* get locked superblock */
if (fstype->fs_flags & FS_REQUIRES_DEV)
sb = get_sb_bdev(fstype, name, flags, data);
else if (fstype->fs_flags & FS_SINGLE)
@@ -1466,10 +1459,7 @@
struct vfsmount *kern_mount(struct file_system_type *type)
{
- char *name = (char *)type->name;
- struct vfsmount *mnt = do_kern_mount(name, 0, name, NULL);
- up(&mount_sem);
- return mnt;
+ return do_kern_mount((char *)type->name, 0, (char *)type->name, NULL);
}
static int do_add_mount(struct nameidata *nd, char *type, int flags,
@@ -1481,6 +1471,7 @@
if (IS_ERR(mnt))
goto out;
+ down(&mount_sem);
/* Something was mounted here while we slept */
while(d_mountpoint(nd->dentry) && follow_down(&nd->mnt, &nd->dentry))
;
@@ -1490,8 +1481,8 @@
retval = -EBUSY;
else
retval = graft_tree(mnt, nd);
- mntput(mnt);
up(&mount_sem);
+ mntput(mnt);
out:
return retval;
}
-
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This archive was generated by hypermail 2b29 : Fri Sep 07 2001 - 21:00:17 EST