fs: add SYNC_FILE_RANGE_BACKGROUND flagfor-4.10/wb-buf-throttle

Allows userspace to submit a range for writeback, but without
the lower levels considering it important.

Signed-off-by: Jens Axboe <axboe@fb.com>

5 files changed, 16 insertions, 8 deletions

diff --git a/fs/sync.c b/fs/sync.c
index 2a54c1f22035..21b5f666e740 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -18,7 +18,7 @@
 #include "internal.h"
 
 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
-			SYNC_FILE_RANGE_WAIT_AFTER)
+			SYNC_FILE_RANGE_WAIT_AFTER|SYNC_FILE_RANGE_BACKGROUND)
 
 /*
  * Do the filesystem syncing work. For simple filesystems
@@ -348,8 +348,10 @@ SYSCALL_DEFINE4(sync_file_range, int, fd, loff_t, offset, loff_t, nbytes,
 	}
 
 	if (flags & SYNC_FILE_RANGE_WRITE) {
+		bool background = flags & SYNC_FILE_RANGE_BACKGROUND;
+
 		ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
-						 WB_SYNC_NONE);
+						 WB_SYNC_NONE, background);
 		if (ret < 0)
 			goto out_put;
 	}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 8533e9d59c29..0076b809f91e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2477,7 +2477,8 @@ 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);
 extern int __filemap_fdatawrite_range(struct address_space *mapping,
-				loff_t start, loff_t end, int sync_mode);
+				loff_t start, loff_t end, int sync_mode,
+				bool background);
 extern int filemap_fdatawrite_range(struct address_space *mapping,
 				loff_t start, loff_t end);
 extern int filemap_check_errors(struct address_space *mapping);
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index c1d11df07b28..9871dc35326b 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -327,6 +327,7 @@ struct fscrypt_policy {
 #define SYNC_FILE_RANGE_WAIT_BEFORE	1
 #define SYNC_FILE_RANGE_WRITE		2
 #define SYNC_FILE_RANGE_WAIT_AFTER	4
+#define SYNC_FILE_RANGE_BACKGROUND	8
 
 /* flags for preadv2/pwritev2: */
 #define RWF_HIPRI			0x00000001 /* high priority request, poll if possible */
diff --git a/mm/fadvise.c b/mm/fadvise.c
index 6c707bfe02fd..37343e814ac8 100644
--- a/mm/fadvise.c
+++ b/mm/fadvise.c
@@ -117,7 +117,7 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
 	case POSIX_FADV_DONTNEED:
 		if (!inode_write_congested(mapping->host))
 			__filemap_fdatawrite_range(mapping, offset, endbyte,
-						   WB_SYNC_NONE);
+						   WB_SYNC_NONE, true);
 
 		/*
 		 * First and last FULL page! Partial pages are deliberately
diff --git a/mm/filemap.c b/mm/filemap.c
index 849f459ad078..026bfa133626 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -363,6 +363,7 @@ EXPORT_SYMBOL(filemap_check_errors);
  * @start:	offset in bytes where the range starts
  * @end:	offset in bytes where the range ends (inclusive)
  * @sync_mode:	enable synchronous operation
+ * @background:	This is a background write operation
  *
  * Start writeback against all of a mapping's dirty pages that lie
  * within the byte offsets <start, end> inclusive.
@@ -373,11 +374,12 @@ EXPORT_SYMBOL(filemap_check_errors);
  * be waited upon, and not just skipped over.
  */
 int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
-				loff_t end, int sync_mode)
+				loff_t end, int sync_mode, bool background)
 {
 	int ret;
 	struct writeback_control wbc = {
 		.sync_mode = sync_mode,
+		.for_background = background,
 		.nr_to_write = LONG_MAX,
 		.range_start = start,
 		.range_end = end,
@@ -395,7 +397,8 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 static inline int __filemap_fdatawrite(struct address_space *mapping,
 	int sync_mode)
 {
-	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
+	return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode,
+						false);
 }
 
 int filemap_fdatawrite(struct address_space *mapping)
@@ -407,7 +410,8 @@ EXPORT_SYMBOL(filemap_fdatawrite);
 int filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
 				loff_t end)
 {
-	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL);
+	return __filemap_fdatawrite_range(mapping, start, end, WB_SYNC_ALL,
+						false);
 }
 EXPORT_SYMBOL(filemap_fdatawrite_range);
 
@@ -578,7 +582,7 @@ int filemap_write_and_wait_range(struct address_space *mapping,
 	if ((!dax_mapping(mapping) && mapping->nrpages) ||
 	    (dax_mapping(mapping) && mapping->nrexceptional)) {
 		err = __filemap_fdatawrite_range(mapping, lstart, lend,
-						 WB_SYNC_ALL);
+						 WB_SYNC_ALL, false);
 		/* See comment of filemap_write_and_wait() */
 		if (err != -EIO) {
 			int err2 = filemap_fdatawait_range(mapping,