fs/ntfs3: Update inode->i_mapping->a_ops on compression state

Update inode->i_mapping->a_ops when the compression state changes to
ensure correct address space operations.
Clear ATTR_FLAG_SPARSED/FILE_ATTRIBUTE_SPARSE_FILE when enabling
compression to prevent flag conflicts.

v2:
Additionally, ensure that all dirty pages are flushed and concurrent access
to the page cache is blocked.

Fixes: 6b39bfa ("fs/ntfs3: Add support for the compression attribute")
Reported-by: Kun Hu <huk23@m.fudan.edu.cn>, Jiaji Qin <jjtan24@m.fudan.edu.cn>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

Author: aalexandrovich

fs/ntfs3/attrib.c

@@ -2664,8 +2664,9 @@ int attr_set_compress(struct ntfs_inode *ni, bool compr)
 		attr->nres.run_off = cpu_to_le16(run_off);
 	}
 
-	/* Update data attribute flags. */
+	/* Update attribute flags. */
 	if (compr) {
+		attr->flags &= ~ATTR_FLAG_SPARSED;
 		attr->flags |= ATTR_FLAG_COMPRESSED;
 		attr->nres.c_unit = NTFS_LZNT_CUNIT;
 	} else {

fs/ntfs3/file.c

@@ -101,8 +101,26 @@ int ntfs_fileattr_set(struct mnt_idmap *idmap, struct dentry *dentry,
 	/* Allowed to change compression for empty files and for directories only. */
 	if (!is_dedup(ni) && !is_encrypted(ni) &&
 	    (S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode))) {
-		/* Change compress state. */
-		int err = ni_set_compress(inode, flags & FS_COMPR_FL);
+		int err = 0;
+		struct address_space *mapping = inode->i_mapping;
+
+		/* write out all data and wait. */
+		filemap_invalidate_lock(mapping);
+		err = filemap_write_and_wait(mapping);
+
+		if (err >= 0) {
+			/* Change compress state. */
+			bool compr = flags & FS_COMPR_FL;
+			err = ni_set_compress(inode, compr);
+
+			/* For files change a_ops too. */
+			if (!err)
+				mapping->a_ops = compr ? &ntfs_aops_cmpr :
+							 &ntfs_aops;
+		}
+
+		filemap_invalidate_unlock(mapping);
+
 		if (err)
 			return err;
 	}

fs/ntfs3/frecord.c

@@ -3434,10 +3434,12 @@ int ni_set_compress(struct inode *inode, bool compr)
 	}
 
 	ni->std_fa = std->fa;
-	if (compr)
+	if (compr) {
+		std->fa &= ~FILE_ATTRIBUTE_SPARSE_FILE;
 		std->fa |= FILE_ATTRIBUTE_COMPRESSED;
-	else
+	} else {
 		std->fa &= ~FILE_ATTRIBUTE_COMPRESSED;
+	}
 
 	if (ni->std_fa != std->fa) {
 		ni->std_fa = std->fa;