[PATCH v3 09/15] smb: client: drain and invalidate before server-side copy/clone

[Paulo Alcantara <pc@manguebit.org>]

cifs_file_copychunk_range() and the clone (FICLONE) path of
cifs_remap_file_range() do not serialise the destination page cache
against the server-side copy the way the other server-side range
operations (smb3_zero_range(), smb3_punch_hole(), smb3_collapse_range()
and smb3_insert_range()) do.

cifs_file_copychunk_range() invalidates the destination range with
filemap_invalidate_inode(), which takes and drops the mapping's
invalidate_lock internally, so the lock is no longer held when the
copychunk ioctl is issued.  It also never drains in-flight netfs I/O on
the target.  The clone path never takes the invalidate_lock at all (only
i_rwsem), uses a bare truncate_inode_pages_range() and likewise does not
drain outstanding I/O.

As a result an asynchronous destination writeback can complete after the
server-side copy/clone has run and reinstate stale data over the region
just written by the server, corrupting the file.  This is the same class
of corruption as commit d7d2adcd022b ("smb/client: flush dirty data
before punching a hole") and has been seen randomly in generic/363
against Windows Server.

Fix both paths to follow the established ordering: hold the target
mapping's invalidate_lock across the flush and invalidation of the
destination and the server ioctl, and call netfs_wait_for_outstanding_io()
on the target to drain in-flight writes before the ioctl is issued.  Only
the target inode's invalidate_lock is required, as the source is merely
flushed and not invalidated; i_rwsem (already held via
lock_two_nondirectories()) is acquired before the invalidate_lock,
matching the VFS lock ordering.  Since filemap_invalidate_inode() takes
that same lock internally, replace it with its own unmap/flush/invalidate
steps instead of calling it, and return early on a zero-length copy to
avoid a range underflow.

Fixes: 8101d6e112e2 ("cifs: Fix copy offload to flush destination region")
Fixes: c54fc3a4f375 ("cifs: Fix flushing, invalidation and file size with FICLONE")
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/smb/client/cifsfs.c | 31 ++++++++++++++++++++++++++-----
 1 file changed, 26 insertions(+), 5 deletions(-)

diff --git a/fs/smb/client/cifsfs.c b/fs/smb/client/cifsfs.c
index 6410249f529a..98b610b2a114 100644
--- a/fs/smb/client/cifsfs.c
+++ b/fs/smb/client/cifsfs.c
@@ -1412,6 +1412,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	 * server could even support copy of range where source = target
 	 */
 	lock_two_nondirectories(target_inode, src_inode);
+	filemap_invalidate_lock(target_inode->i_mapping);
 
 	if (len == 0) {
 		loff_t src_size = i_size_read(src_inode);
@@ -1475,6 +1476,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	cifs_dbg(FYI, "about to discard pages %llx-%llx\n", fstart, fend);
 	truncate_inode_pages_range(&target_inode->i_data,
 				   min(fstart, i_size), fend);
+	netfs_wait_for_outstanding_io(target_inode);
 
 	fscache_invalidate(cifs_inode_cookie(target_inode), NULL, i_size, 0);
 
@@ -1513,6 +1515,7 @@ static loff_t cifs_remap_file_range(struct file *src_file, loff_t off,
 	if (rc)
 		CIFS_I(target_inode)->time = 0;
 unlock:
+	filemap_invalidate_unlock(target_inode->i_mapping);
 	/* although unlocking in the reverse order from locking is not
 	   strictly necessary here it is a little cleaner to be consistent */
 	unlock_two_nondirectories(src_inode, target_inode);
@@ -1536,6 +1539,9 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	struct cifs_tcon *target_tcon;
 	ssize_t rc;
 
+	if (len == 0)
+		return 0;
+
 	cifs_dbg(FYI, "copychunk range\n");
 
 	if (!src_file->private_data || !dst_file->private_data) {
@@ -1565,6 +1571,7 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	 * server could even support copy of range where source = target
 	 */
 	lock_two_nondirectories(target_inode, src_inode);
+	filemap_invalidate_lock(target_inode->i_mapping);
 
 	cifs_dbg(FYI, "about to flush pages\n");
 
@@ -1590,11 +1597,24 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	 * Start at the old EOF when extending so the folio straddling it, which
 	 * may hold data written past EOF through an mmap, is dropped too.
 	 */
-	rc = filemap_invalidate_inode(target_inode, true,
-				      min(destoff, i_size_read(target_inode)),
-				      destoff + len - 1);
-	if (rc)
-		goto unlock;
+	if (target_inode->i_mapping->nrpages) {
+		loff_t fstart = min(destoff, i_size_read(target_inode));
+		loff_t fend = destoff + len - 1;
+
+		unmap_mapping_pages(target_inode->i_mapping,
+				    fstart >> PAGE_SHIFT,
+				    (fend >> PAGE_SHIFT) -
+				    (fstart >> PAGE_SHIFT) + 1,
+				    false);
+		rc = filemap_write_and_wait_range(target_inode->i_mapping,
+						  fstart, fend);
+		if (rc)
+			goto unlock;
+		invalidate_inode_pages2_range(target_inode->i_mapping,
+					      fstart >> PAGE_SHIFT,
+					      fend >> PAGE_SHIFT);
+	}
+	netfs_wait_for_outstanding_io(target_inode);
 
 	fscache_invalidate(cifs_inode_cookie(target_inode), NULL,
 			   i_size_read(target_inode), 0);
@@ -1626,6 +1646,7 @@ ssize_t cifs_file_copychunk_range(unsigned int xid,
 	CIFS_I(target_inode)->time = 0;
 
 unlock:
+	filemap_invalidate_unlock(target_inode->i_mapping);
 	/* although unlocking in the reverse order from locking is not
 	 * strictly necessary here it is a little cleaner to be consistent
 	 */
-- 
2.55.0