[PATCH 06/12] zonefs: Convert to using invalidate_lock

[Jan Kara <jack@suse.cz>]

Use invalidate_lock instead of zonefs' private i_mmap_sem. The intended
purpose is exactly the same. By this conversion we also fix a race
between hole punching and read(2) / readahead(2) paths that can lead to
stale page cache contents.

CC: Damien Le Moal <damien.lemoal@wdc.com>
CC: Johannes Thumshirn <jth@kernel.org>
CC: <linux-fsdevel@vger.kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/zonefs/super.c  | 23 +++++------------------
 fs/zonefs/zonefs.h |  7 +++----
 2 files changed, 8 insertions(+), 22 deletions(-)

diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c
index 049e36c69ed7..60ac5587c880 100644
--- a/fs/zonefs/super.c
+++ b/fs/zonefs/super.c
@@ -462,7 +462,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
 	inode_dio_wait(inode);
 
 	/* Serialize against page faults */
-	down_write(&zi->i_mmap_sem);
+	down_write(&inode->i_mapping->invalidate_lock);
 
 	/* Serialize against zonefs_iomap_begin() */
 	mutex_lock(&zi->i_truncate_mutex);
@@ -500,7 +500,7 @@ static int zonefs_file_truncate(struct inode *inode, loff_t isize)
 
 unlock:
 	mutex_unlock(&zi->i_truncate_mutex);
-	up_write(&zi->i_mmap_sem);
+	up_write(&inode->i_mapping->invalidate_lock);
 
 	return ret;
 }
@@ -575,18 +575,6 @@ static int zonefs_file_fsync(struct file *file, loff_t start, loff_t end,
 	return ret;
 }
 
-static vm_fault_t zonefs_filemap_fault(struct vm_fault *vmf)
-{
-	struct zonefs_inode_info *zi = ZONEFS_I(file_inode(vmf->vma->vm_file));
-	vm_fault_t ret;
-
-	down_read(&zi->i_mmap_sem);
-	ret = filemap_fault(vmf);
-	up_read(&zi->i_mmap_sem);
-
-	return ret;
-}
-
 static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
 {
 	struct inode *inode = file_inode(vmf->vma->vm_file);
@@ -607,16 +595,16 @@ static vm_fault_t zonefs_filemap_page_mkwrite(struct vm_fault *vmf)
 	file_update_time(vmf->vma->vm_file);
 
 	/* Serialize against truncates */
-	down_read(&zi->i_mmap_sem);
+	down_read(&inode->i_mapping->invalidate_lock);
 	ret = iomap_page_mkwrite(vmf, &zonefs_iomap_ops);
-	up_read(&zi->i_mmap_sem);
+	up_read(&inode->i_mapping->invalidate_lock);
 
 	sb_end_pagefault(inode->i_sb);
 	return ret;
 }
 
 static const struct vm_operations_struct zonefs_file_vm_ops = {
-	.fault		= zonefs_filemap_fault,
+	.fault		= filemap_fault,
 	.map_pages	= filemap_map_pages,
 	.page_mkwrite	= zonefs_filemap_page_mkwrite,
 };
@@ -1158,7 +1146,6 @@ static struct inode *zonefs_alloc_inode(struct super_block *sb)
 
 	inode_init_once(&zi->i_vnode);
 	mutex_init(&zi->i_truncate_mutex);
-	init_rwsem(&zi->i_mmap_sem);
 	zi->i_wr_refcnt = 0;
 
 	return &zi->i_vnode;
diff --git a/fs/zonefs/zonefs.h b/fs/zonefs/zonefs.h
index 51141907097c..7b147907c328 100644
--- a/fs/zonefs/zonefs.h
+++ b/fs/zonefs/zonefs.h
@@ -70,12 +70,11 @@ struct zonefs_inode_info {
 	 * and changes to the inode private data, and in particular changes to
 	 * a sequential file size on completion of direct IO writes.
 	 * Serialization of mmap read IOs with truncate and syscall IO
-	 * operations is done with i_mmap_sem in addition to i_truncate_mutex.
-	 * Only zonefs_seq_file_truncate() takes both lock (i_mmap_sem first,
-	 * i_truncate_mutex second).
+	 * operations is done with invalidate_lock in addition to
+	 * i_truncate_mutex.  Only zonefs_seq_file_truncate() takes both lock
+	 * (invalidate_lock first, i_truncate_mutex second).
 	 */
 	struct mutex		i_truncate_mutex;
-	struct rw_semaphore	i_mmap_sem;
 
 	/* guarded by i_truncate_mutex */
 	unsigned int		i_wr_refcnt;
-- 
2.26.2