Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxxxxxxxx>
---
include/linux/fs.h | 2 ++
mm/mmap.c | 13 ++++++++++++-
mm/revoke.c | 18 +++++++++++++++---
3 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 76041b6..5d3d6b8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -633,6 +633,8 @@ struct address_space {
const struct address_space_operations *a_ops; /* methods */
unsigned long flags; /* error bits/gfp mask */
struct backing_dev_info *backing_dev_info; /* device readahead, etc */
+ struct task_struct *revoke_task; /* Who to wake up when all vmas are closed */
+ unsigned int close_count; /* Cover race conditions with revoke_mappings */
spinlock_t private_lock; /* for use by the address_space */
struct list_head private_list; /* ditto */
struct address_space *assoc_mapping; /* ditto */
diff --git a/mm/mmap.c b/mm/mmap.c
index 17dd003..3df3193 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -218,6 +218,7 @@ void unlink_file_vma(struct vm_area_struct *vma)
struct address_space *mapping = file->f_mapping;
spin_lock(&mapping->i_mmap_lock);
__remove_shared_vm_struct(vma, file, mapping);
+ mapping->close_count++;
spin_unlock(&mapping->i_mmap_lock);
}
}
@@ -233,9 +234,19 @@ static struct vm_area_struct *remove_vma(struct vm_area_struct *vma)
if (vma->vm_ops && vma->vm_ops->close)
vma->vm_ops->close(vma);
if (vma->vm_file) {
- fput(vma->vm_file);
+ struct address_space *mapping = vma->vm_file->f_mapping;
if (vma->vm_flags & VM_EXECUTABLE)
removed_exe_file_vma(vma->vm_mm);
+
+ /* Decrement the close count and wake up a revoker if present */
+ spin_lock(&mapping->i_mmap_lock);
+ mapping->close_count--;
+ if ((mapping->close_count == 0) && mapping->revoke_task)
+ /* Is wake_up_process the right variant of try_to_wake_up? */
+ wake_up_process(mapping->revoke_task);
+ spin_unlock(&mapping->i_mmap_lock);
+
+ fput(vma->vm_file);
}
mpol_put(vma_policy(vma));
kmem_cache_free(vm_area_cachep, vma);
diff --git a/mm/revoke.c b/mm/revoke.c
index a76cd1a..e19f7df 100644
--- a/mm/revoke.c
+++ b/mm/revoke.c
@@ -143,15 +143,17 @@ void revoke_mappings(struct address_space *mapping)
/* Make any access to previously mapped pages trigger a SIGBUS,
* and stop calling vm_ops methods.
*
- * When revoke_mappings returns invocations of vm_ops->close
- * may still be in progress, but no invocations of any other
- * vm_ops methods will be.
+ * When revoke_mappings no invocations of any method will be
+ * in progress.
*/
struct vm_area_struct *vma;
struct prio_tree_iter iter;
spin_lock(&mapping->i_mmap_lock);
+ WARN_ON(mapping->revoke_task);
+ mapping->revoke_task = current;
+
restart_tree:
vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX) {
if (revoke_mapping(mapping, vma->vm_mm, vma->vm_start))
@@ -164,6 +166,16 @@ restart_list:
goto restart_list;
}
+ while (!list_empty(&mapping->i_mmap_nonlinear) ||
+ !prio_tree_empty(&mapping->i_mmap) ||
+ mapping->close_count)
+ {
+ __set_current_state(TASK_UNINTERRUPTIBLE);
+ spin_unlock(&mapping->i_mmap_lock);
+ schedule();
+ spin_lock(&mapping->i_mmap_lock);
+ }
+ mapping->revoke_task = NULL;
spin_unlock(&mapping->i_mmap_lock);
}
EXPORT_SYMBOL_GPL(revoke_mappings);
--
1.7.2.3
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