svn commit: r300371 - head/sys/fs/msdosfs

[Konstantin Belousov]

Author: kib
Date: Sat May 21 11:40:41 2016
New Revision: 300371
URL: https://svnweb.freebsd.org/changeset/base/300371

Log:
  Same as for UFS, remove drop/reacquire of Giant, and use si_mountpt as
  the mount semaphore.
  
  Sponsored by: The FreeBSD Foundation
  MFC after:    2 weeks

Modified:
  head/sys/fs/msdosfs/msdosfs_vfsops.c

Modified: head/sys/fs/msdosfs/msdosfs_vfsops.c
==============================================================================
--- head/sys/fs/msdosfs/msdosfs_vfsops.c        Sat May 21 11:26:03 2016        
(r300370)
+++ head/sys/fs/msdosfs/msdosfs_vfsops.c        Sat May 21 11:40:41 2016        
(r300371)
@@ -292,11 +292,9 @@ msdosfs_mount(struct mount *mp)
                        }
 
                        /* Downgrade the device from rw to ro. */
-                       DROP_GIANT();
                        g_topology_lock();
                        error = g_access(pmp->pm_cp, 0, -1, 0);
                        g_topology_unlock();
-                       PICKUP_GIANT();
                        if (error) {
                                (void)markvoldirty(pmp, 1);
                                return (error);
@@ -328,11 +326,9 @@ msdosfs_mount(struct mount *mp)
                                return (error);
                        }
                        VOP_UNLOCK(devvp, 0);
-                       DROP_GIANT();
                        g_topology_lock();
                        error = g_access(pmp->pm_cp, 0, 1, 0);
                        g_topology_unlock();
-                       PICKUP_GIANT();
                        if (error)
                                return (error);
 
@@ -401,8 +397,6 @@ msdosfs_mount(struct mount *mp)
                return error;
        }
 
-       if (devvp->v_type == VCHR && devvp->v_rdev != NULL)
-               devvp->v_rdev->si_mountpt = mp;
        vfs_mountedfrom(mp, from);
 #ifdef MSDOSFS_DEBUG
        printf("msdosfs_mount(): mp %p, pmp %p, inusemap %p\n", mp, pmp, 
pmp->pm_inusemap);
@@ -431,15 +425,21 @@ mountmsdosfs(struct vnode *devvp, struct
        ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
 
        dev = devvp->v_rdev;
-       dev_ref(dev);
-       DROP_GIANT();
+       if (atomic_cmpset_acq_ptr((uintptr_t *)&dev->si_mountpt, 0,
+           (uintptr_t)mp) == 0) {
+               VOP_UNLOCK(devvp, 0);
+               return (EBUSY);
+       }
        g_topology_lock();
        error = g_vfs_open(devvp, &cp, "msdosfs", ronly ? 0 : 1);
        g_topology_unlock();
-       PICKUP_GIANT();
+       if (error != 0) {
+               atomic_store_rel_ptr((uintptr_t *)&dev->si_mountpt, 0);
+               VOP_UNLOCK(devvp, 0);
+               return (error);
+       }
+       dev_ref(dev);
        VOP_UNLOCK(devvp, 0);
-       if (error)
-               goto error_exit;
 
        bo = &devvp->v_bufobj;
 
@@ -770,11 +770,9 @@ error_exit:
        if (bp)
                brelse(bp);
        if (cp != NULL) {
-               DROP_GIANT();
                g_topology_lock();
                g_vfs_close(cp);
                g_topology_unlock();
-               PICKUP_GIANT();
        }
        if (pmp) {
                lockdestroy(&pmp->pm_fatlock);
@@ -783,6 +781,7 @@ error_exit:
                free(pmp, M_MSDOSFSMNT);
                mp->mnt_data = NULL;
        }
+       atomic_store_rel_ptr((uintptr_t *)&dev->si_mountpt, 0);
        dev_rel(dev);
        return (error);
 }
@@ -846,13 +845,10 @@ msdosfs_unmount(struct mount *mp, int mn
                BO_UNLOCK(bo);
        }
 #endif
-       DROP_GIANT();
-       if (pmp->pm_devvp->v_type == VCHR && pmp->pm_devvp->v_rdev != NULL)
-               pmp->pm_devvp->v_rdev->si_mountpt = NULL;
        g_topology_lock();
        g_vfs_close(pmp->pm_cp);
        g_topology_unlock();
-       PICKUP_GIANT();
+       atomic_store_rel_ptr((uintptr_t *)&pmp->pm_dev->si_mountpt, 0);
        vrele(pmp->pm_devvp);
        dev_rel(pmp->pm_dev);
        free(pmp->pm_inusemap, M_MSDOSFSFAT);
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