[RFC PATCH 08/10] mm/gup: fs: Send SIGBUS on truncate of active file

[ira . weiny]

From: Ira Weiny <ira.we...@intel.com>

Now that the taking of LONGTERM leases is in place we can now facilitate
sending a SIGBUS to process if a file truncate or hole punch is
performed and they do not respond by releasing the lease.

The standard file lease_break_time is used to time out the LONGTERM
lease which is in place on the inode.
---
 fs/ext4/inode.c    |  4 ++++
 fs/locks.c         | 13 +++++++++++--
 fs/xfs/xfs_file.c  |  4 ++++
 include/linux/fs.h | 13 +++++++++++++
 4 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b32a57bc5d5d..bee456c8c805 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4237,6 +4237,10 @@ int ext4_break_layouts(struct inode *inode)
        if (WARN_ON_ONCE(!rwsem_is_locked(&ei->i_mmap_sem)))
                return -EINVAL;
 
+       /* Break longterm leases */
+       if (dax_mapping_is_dax(inode->i_mapping))
+               break_longterm(inode);
+
        do {
                page = dax_layout_busy_page(inode->i_mapping);
                if (!page)
diff --git a/fs/locks.c b/fs/locks.c
index 58c6d7a411b6..c77eee081d11 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -1580,6 +1580,7 @@ static void time_out_leases(struct inode *inode, struct 
list_head *dispose)
 {
        struct file_lock_context *ctx = inode->i_flctx;
        struct file_lock *fl, *tmp;
+       struct task_struct *tsk;
 
        lockdep_assert_held(&ctx->flc_lock);
 
@@ -1587,8 +1588,16 @@ static void time_out_leases(struct inode *inode, struct 
list_head *dispose)
                trace_time_out_leases(inode, fl);
                if (past_time(fl->fl_downgrade_time))
                        lease_modify(fl, F_RDLCK, dispose);
-               if (past_time(fl->fl_break_time))
-                       lease_modify(fl, F_UNLCK, dispose);
+               if (past_time(fl->fl_break_time)) {
+                       if (fl->fl_flags & FL_LONGTERM) {
+                               tsk = find_task_by_vpid(fl->fl_pid);
+                               fl->fl_break_time = 1 + jiffies + 
lease_break_time * HZ;
+                               lease_modify_longterm(fl, F_UNLCK, dispose);
+                               kill_pid(tsk->thread_pid, SIGBUS, 0);
+                       } else {
+                               lease_modify(fl, F_UNLCK, dispose);
+                       }
+               }
        }
 }
 
diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 1f2e2845eb76..ebd310f3ae65 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -739,6 +739,10 @@ xfs_break_dax_layouts(
 
        ASSERT(xfs_isilocked(XFS_I(inode), XFS_MMAPLOCK_EXCL));
 
+       /* Break longterm leases */
+       if (dax_mapping_is_dax(inode->i_mapping))
+               break_longterm(inode);
+
        page = dax_layout_busy_page(inode->i_mapping);
        if (!page)
                return 0;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index be2d08080aa5..0e8b21240a71 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2459,6 +2459,14 @@ static inline int break_layout(struct inode *inode, bool 
wait)
        return 0;
 }
 
+static inline int break_longterm(struct inode *inode)
+{
+       smp_mb();
+       if (inode->i_flctx && !list_empty_careful(&inode->i_flctx->flc_lease))
+               return __break_lease(inode, O_WRONLY, FL_LONGTERM);
+       return 0;
+}
+
 #else /* !CONFIG_FILE_LOCKING */
 static inline int break_lease(struct inode *inode, unsigned int mode)
 {
@@ -2486,6 +2494,11 @@ static inline int break_layout(struct inode *inode, bool 
wait)
        return 0;
 }
 
+static inline int break_longterm(struct inode *inode, bool wait)
+{
+       return 0;
+}
+
 #endif /* CONFIG_FILE_LOCKING */
 
 /* fs/open.c */
-- 
2.20.1