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From:   Ross Zwisler <zwisler@chromium.org>
To:     linux-kernel@vger.kernel.org
Cc:     Ross Zwisler <zwisler@google.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jan Kara <jack@suse.com>, linux-ext4@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        Fletcher Woodruff <fletcherw@google.com>,
        Justin TerAvest <teravest@google.com>
Subject: [PATCH 1/3] mm: add filemap_fdatawait_range_keep_errors()
Date:   Wed, 19 Jun 2019 11:21:54 -0600
Message-Id: <20190619172156.105508-2-zwisler@google.com>
In-Reply-To: <20190619172156.105508-1-zwisler@google.com>
References: <20190619172156.105508-1-zwisler@google.com>
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Sender: linux-ext4-owner@vger.kernel.org
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In the spirit of filemap_fdatawait_range() and
filemap_fdatawait_keep_errors(), introduce
filemap_fdatawait_range_keep_errors() which both takes a range upon
which to wait and does not clear errors from the address space.

Signed-off-by: Ross Zwisler <zwisler@google.com>
---
 include/linux/fs.h |  2 ++
 mm/filemap.c       | 22 ++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f7fdfe93e25d3..79fec8a8413f4 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2712,6 +2712,8 @@ extern int filemap_flush(struct address_space *);
 extern int filemap_fdatawait_keep_errors(struct address_space *mapping);
 extern int filemap_fdatawait_range(struct address_space *, loff_t lstart,
 				   loff_t lend);
+extern int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
+		loff_t start_byte, loff_t end_byte);
 
 static inline int filemap_fdatawait(struct address_space *mapping)
 {
diff --git a/mm/filemap.c b/mm/filemap.c
index df2006ba0cfa5..e87252ca0835a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -553,6 +553,28 @@ int filemap_fdatawait_range(struct address_space *mapping, loff_t start_byte,
 }
 EXPORT_SYMBOL(filemap_fdatawait_range);
 
+/**
+ * filemap_fdatawait_range_keep_errors - wait for writeback to complete
+ * @mapping:		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 given address space in the
+ * given range and wait for all of them.  Unlike filemap_fdatawait_range(),
+ * this function does not clear error status of the address space.
+ *
+ * Use this function if callers don't handle errors themselves.  Expected
+ * call sites are system-wide / filesystem-wide data flushers: e.g. sync(2),
+ * fsfreeze(8)
+ */
+int filemap_fdatawait_range_keep_errors(struct address_space *mapping,
+		loff_t start_byte, loff_t end_byte)
+{
+	__filemap_fdatawait_range(mapping, start_byte, end_byte);
+	return filemap_check_and_keep_errors(mapping);
+}
+EXPORT_SYMBOL(filemap_fdatawait_range_keep_errors);
+
 /**
  * file_fdatawait_range - wait for writeback to complete
  * @file:		file pointing to address space structure to wait for
-- 
2.22.0.410.gd8fdbe21b5-goog