[Devel] [PATCH RHEL7 COMMIT] ms/mm: add file_fdatawait_range and file_write_and_wait

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-862.3.2.vz7.61.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-862.3.2.vz7.61.3
------>
commit 868b21a2f9f7a38f0de85e28bd76731bcd00e10d
Author: Vasily Averin <vvs at virtuozzo.com>
Date:   Mon Jun 18 12:02:03 2018 +0300

    ms/mm: add file_fdatawait_range and file_write_and_wait
    
    Necessary now for gfs2_fsync and sync_file_range, but there will
    eventually be other callers.
    
    Reviewed-by: Jan Kara <jack at suse.cz>
    Signed-off-by: Jeff Layton <jlayton at redhat.com>
    
    https://pmc.acronis.com/browse/VSTOR-10912
    (cherry picked from commit a823e4589e68996436d16db4ede9a43b646332f9)
    Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
 include/linux/fs.h |  9 ++++++++-
 mm/filemap.c       | 23 +++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4290c8957aab..340770ef3c86 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2960,12 +2960,19 @@ extern int __filemap_fdatawrite_range(struct address_space *mapping,
 extern int filemap_fdatawrite_range(struct address_space *mapping,
 				loff_t start, loff_t end);
 extern int filemap_check_errors(struct address_space *mapping);
-
 extern void __filemap_set_wb_err(struct address_space *mapping, int err);
+
+extern int __must_check file_fdatawait_range(struct file *file, loff_t lstart,
+						loff_t lend);
 extern int __must_check file_check_and_advance_wb_err(struct file *file);
 extern int __must_check file_write_and_wait_range(struct file *file,
 						loff_t start, loff_t end);
 
+static inline int file_write_and_wait(struct file *file)
+{
+	return file_write_and_wait_range(file, 0, LLONG_MAX);
+}
+
 /**
  * filemap_set_wb_err - set a writeback error on an address_space
  * @mapping: mapping in which to set writeback error
diff --git a/mm/filemap.c b/mm/filemap.c
index 4da330109568..f4db0e7e40bd 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -446,6 +446,29 @@ int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 }
 EXPORT_SYMBOL(filemap_fdatawait_range);
 
+/**
+ * file_fdatawait_range - wait for writeback to complete
+ * @file:		file pointing to address space structure to wait for
+ * @start_byte:		offset in bytes where the range starts
+ * @end_byte:		offset in bytes where the range ends (inclusive)
+ *
+ * Walk the list of under-writeback pages of the address space that file
+ * refers to, in the given range and wait for all of them.  Check error
+ * status of the address space vs. the file->f_wb_err cursor and return it.
+ *
+ * Since the error status of the file is advanced by this function,
+ * callers are responsible for checking the return value and handling and/or
+ * reporting the error.
+ */
+int file_fdatawait_range(struct file *file, loff_t start_byte, loff_t end_byte)
+{
+	struct address_space *mapping = file->f_mapping;
+
+	__filemap_fdatawait_range(mapping, start_byte, end_byte);
+	return file_check_and_advance_wb_err(file);
+}
+EXPORT_SYMBOL(file_fdatawait_range);
+
 /**
  * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
  * @mapping: address space structure to wait for