[PATCH 2/2] fs: wire up .truncate_range and .fallocate

[Cong Wang <amwang@redhat.com>]

As Hugh suggested, with FALLOC_FL_PUNCH_HOLE, we can use do_fallocate()
to implement madvise_remove and finally remove .truncate_range call back.

Cc: Hugh Dickins <hughd@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: WANG Cong <amwang@redhat.com>

---
 include/linux/fs.h |    1 -
 include/linux/mm.h |    3 ++-
 mm/madvise.c       |    8 +++++---
 mm/shmem.c         |    1 -
 mm/truncate.c      |   21 +++++++++++++--------
 5 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e313022..266df73 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1635,7 +1635,6 @@ struct inode_operations {
 	ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
 	ssize_t (*listxattr) (struct dentry *, char *, size_t);
 	int (*removexattr) (struct dentry *, const char *);
-	void (*truncate_range)(struct inode *, loff_t, loff_t);
 	int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start,
 		      u64 len);
 } ____cacheline_aligned;
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3dc3a8c..a47f744 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -951,7 +951,8 @@ static inline void unmap_shared_mapping_range(struct address_space *mapping,
 extern void truncate_pagecache(struct inode *inode, loff_t old, loff_t new);
 extern void truncate_setsize(struct inode *inode, loff_t newsize);
 extern int vmtruncate(struct inode *inode, loff_t offset);
-extern int vmtruncate_range(struct inode *inode, loff_t offset, loff_t end);
+extern int vmtruncate_file_range(struct file *file, struct inode *inode,
+			loff_t offset, loff_t end);
 
 int truncate_inode_page(struct address_space *mapping, struct page *page);
 int generic_error_remove_page(struct address_space *mapping, struct page *page);
diff --git a/mm/madvise.c b/mm/madvise.c
index 74bf193..05610d3 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -194,7 +194,8 @@ static long madvise_remove(struct vm_area_struct *vma,
 				struct vm_area_struct **prev,
 				unsigned long start, unsigned long end)
 {
-	struct address_space *mapping;
+	struct file *file;
+	struct inode *inode;
 	loff_t offset, endoff;
 	int error;
 
@@ -211,7 +212,8 @@ static long madvise_remove(struct vm_area_struct *vma,
 	if ((vma->vm_flags & (VM_SHARED|VM_WRITE)) != (VM_SHARED|VM_WRITE))
 		return -EACCES;
 
-	mapping = vma->vm_file->f_mapping;
+	file = vma->vm_file;
+	inode = file->f_mapping->host;
 
 	offset = (loff_t)(start - vma->vm_start)
 			+ ((loff_t)vma->vm_pgoff << PAGE_SHIFT);
@@ -220,7 +222,7 @@ static long madvise_remove(struct vm_area_struct *vma,
 
 	/* vmtruncate_range needs to take i_mutex */
 	up_read(&current->mm->mmap_sem);
-	error = vmtruncate_range(mapping->host, offset, endoff);
+	error = vmtruncate_file_range(file, inode, offset, endoff);
 	down_read(&current->mm->mmap_sem);
 	return error;
 }
diff --git a/mm/shmem.c b/mm/shmem.c
index 65f7a27..fce5667 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2356,7 +2356,6 @@ static const struct file_operations shmem_file_operations = {
 
 static const struct inode_operations shmem_inode_operations = {
 	.setattr	= shmem_setattr,
-	.truncate_range	= shmem_truncate_range,
 #ifdef CONFIG_TMPFS_XATTR
 	.setxattr	= shmem_setxattr,
 	.getxattr	= shmem_getxattr,
diff --git a/mm/truncate.c b/mm/truncate.c
index 632b15e..7c46539 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -20,6 +20,7 @@
 #include <linux/buffer_head.h>	/* grr. try_to_release_page,
 				   do_invalidatepage */
 #include <linux/cleancache.h>
+#include <linux/falloc.h>
 #include "internal.h"
 
 
@@ -602,24 +603,28 @@ int vmtruncate(struct inode *inode, loff_t newsize)
 }
 EXPORT_SYMBOL(vmtruncate);
 
-int vmtruncate_range(struct inode *inode, loff_t lstart, loff_t lend)
+int vmtruncate_file_range(struct file *file, struct inode *inode,
+		     loff_t lstart, loff_t lend)
 {
 	struct address_space *mapping = inode->i_mapping;
 	loff_t holebegin = round_up(lstart, PAGE_SIZE);
 	loff_t holelen = 1 + lend - holebegin;
+	int err;
 
-	/*
-	 * If the underlying filesystem is not going to provide
-	 * a way to truncate a range of blocks (punch a hole) -
-	 * we should return failure right now.
-	 */
-	if (!inode->i_op->truncate_range)
+	if (!file->f_op->fallocate)
 		return -ENOSYS;
 
 	mutex_lock(&inode->i_mutex);
 	inode_dio_wait(inode);
 	unmap_mapping_range(mapping, holebegin, holelen, 1);
-	inode->i_op->truncate_range(inode, lstart, lend);
+	mutex_unlock(&inode->i_mutex);
+
+	err = do_fallocate(file, FALLOC_FL_KEEP_SIZE|FALLOC_FL_PUNCH_HOLE,
+		     holebegin, holelen);
+	if (err)
+		return err;
+
+	mutex_lock(&inode->i_mutex);
 	/* unmap again to remove racily COWed private pages */
 	unmap_mapping_range(mapping, holebegin, holelen, 1);
 	mutex_unlock(&inode->i_mutex);
-- 
1.7.4.4

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