[PATCH] fs: convert sync_file_range to use errseq_t based error-tracking

[Jeff Layton]

From: Jeff Layton <jlayton@xxxxxxxxxx>

sync_file_range doesn't call down into the filesystem directly at all.
It only kicks off writeback of pagecache pages and optionally waits
on the result.

Convert sync_file_range to use errseq_t based error tracking, under the
assumption that most users will prefer this behavior when errors occur.

Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
 fs/sync.c          |  4 ++--
 include/linux/fs.h |  2 ++
 mm/filemap.c       | 22 ++++++++++++++++++++++
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/fs/sync.c b/fs/sync.c
index 2a54c1f22035..27d6b8bbcb6a 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -342,7 +342,7 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 
 	ret = 0;
 	if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
-		ret = filemap_fdatawait_range(mapping, offset, endbyte);
+		ret = file_fdatawait_range(f.file, offset, endbyte);
 		if (ret < 0)
 			goto out_put;
 	}
@@ -355,7 +355,7 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 	}
 
 	if (flags & SYNC_FILE_RANGE_WAIT_AFTER)
-		ret = filemap_fdatawait_range(mapping, offset, endbyte);
+		ret = file_fdatawait_range(f.file, offset, endbyte);
 
 out_put:
 	fdput(f);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7b5d6816542b..fb615e1eb1d4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2544,6 +2544,8 @@ extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
 				   loff_t lend);
 extern bool filemap_range_has_page(struct address_space *, loff_t lstart,
 				  loff_t lend);
+extern int __must_check file_fdatawait_range(struct file *file, loff_t lstart,
+						loff_t lend);
 extern int filemap_write_and_wait(struct address_space *mapping);
 extern int filemap_write_and_wait_range(struct address_space *mapping,
 				        loff_t lstart, loff_t lend);
diff --git a/mm/filemap.c b/mm/filemap.c
index a49702445ce0..bb17590d7c67 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -476,6 +476,28 @@ 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);
+}
+
+/**
  * filemap_fdatawait_keep_errors - wait for writeback without clearing errors
  * @mapping: address space structure to wait for
  *
-- 
2.13.3