@@ -235,9 +235,9 @@ SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
}
/*
- * sys_sync_file_range() permits finely controlled syncing over a segment of
+ * ksys_sync_file_range() permits finely controlled syncing over a segment of
* a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
- * zero then sys_sync_file_range() will operate from offset out to EOF.
+ * zero then ksys_sync_file_range() will operate from offset out to EOF.
*
* The flag bits are:
*
@@ -254,7 +254,7 @@ SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
* Useful combinations of the flag bits are:
*
* SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
- * in the range which were dirty on entry to sys_sync_file_range() are placed
+ * in the range which were dirty on entry to ksys_sync_file_range() are placed
* under writeout. This is a start-write-for-data-integrity operation.
*
* SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
@@ -266,10 +266,13 @@ SYSCALL_DEFINE1(fdatasync, unsigned int, fd)
* earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
* for that operation to complete and to return the result.
*
- * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
+ * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER
+ * (a.k.a. SYNC_FILE_RANGE_WRITE_AND_WAIT):
* a traditional sync() operation. This is a write-for-data-integrity operation
* which will ensure that all pages in the range which were dirty on entry to
- * sys_sync_file_range() are committed to disk.
+ * ksys_sync_file_range() are written to disk. It should be noted that disk
+ * caches are not flushed by this call, so there are no guarantees here that the
+ * data will be available on disk after a crash.
*
*
* SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
@@ -345,8 +348,14 @@ int ksys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
}
if (flags & SYNC_FILE_RANGE_WRITE) {
+ int sync_mode = WB_SYNC_NONE;
+
+ if ((flags & SYNC_FILE_RANGE_WRITE_AND_WAIT) ==
+ SYNC_FILE_RANGE_WRITE_AND_WAIT)
+ sync_mode = WB_SYNC_ALL;
+
ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
- WB_SYNC_NONE);
+ sync_mode);
if (ret < 0)
goto out_put;
}
@@ -320,6 +320,9 @@ struct fscrypt_key {
#define SYNC_FILE_RANGE_WAIT_BEFORE 1
#define SYNC_FILE_RANGE_WRITE 2
#define SYNC_FILE_RANGE_WAIT_AFTER 4
+#define SYNC_FILE_RANGE_WRITE_AND_WAIT (SYNC_FILE_RANGE_WRITE | \
+ SYNC_FILE_RANGE_WAIT_BEFORE | \
+ SYNC_FILE_RANGE_WAIT_AFTER)
/*
* Flags for preadv2/pwritev2:
Commit 23d0127096cb ("fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE writeback") claims that sync_file_range(2) syscall was "created for userspace to be able to issue background writeout and so waiting for in-flight IO is undesirable there" and changes the writeback (back) to WB_SYNC_NONE. This claim is only partially true. It is true for users that use the flag SYNC_FILE_RANGE_WRITE by itself, as does PostgreSQL, the user that was the reason for changing to WB_SYNC_NONE writeback. However, that claim is not true for users that use that flag combination SYNC_FILE_RANGE_{WAIT_BEFORE|WRITE|_WAIT_AFTER}. Those users explicitly requested to wait for in-flight IO as well as to writeback of dirty pages. Re-brand that flag combination as SYNC_FILE_RANGE_WRITE_AND_WAIT and use WB_SYNC_ALL writeback to perform the full range sync request. Link: http://lkml.kernel.org/r/20190409114922.30095-1-amir73il@gmail.com Fixes: 23d0127096cb ("fs/sync.c: make sync_file_range(2) use WB_SYNC_NONE") Signed-off-by: Amir Goldstein <amir73il@gmail.com> Acked-by: Jan Kara <jack@suse.com> Cc: Dave Chinner <david@fromorbit.com> Cc: Al Viro <viro@zeniv.linux.org.uk> --- Andrew, One more version addressing another comment by Dave Chinner. Thanks, Amir. Changes since v4: - Don't use filemap_write_and_wait_range() helper (Dave) Changes since v3: - Remove unneeded change to VALID_FLAGS (Dave) - Call file_fdatawait_range() before writeback (Dave) Changes since v2: - Return after filemap_write_and_wait_range() Changes since v1: - Remove non-guaranties of the API from commit message - Added ACK by Jan fs/sync.c | 21 +++++++++++++++------ include/uapi/linux/fs.h | 3 +++ 2 files changed, 18 insertions(+), 6 deletions(-)