1SYNC_FILE_RANGE(2) Linux Programmer's Manual SYNC_FILE_RANGE(2)
2
6 sync_file_range - sync a file segment with disk
7
9 #define _GNU_SOURCE
10 #include <fcntl.h>
11 int sync_file_range(int fd, off64_t offset, off64_t nbytes,
13 unsigned int flags);
14
16 sync_file_range() permits fine control when synchronizing the open file
17 referred to by the file descriptor fd with disk.
18 offset is the starting byte of the file range to be synchronized.
20 nbytes specifies the length of the range to be synchronized, in bytes;
21 if nbytes is zero, then all bytes from offset through to the end of
22 file are synchronized. Synchronization is in units of the system page
23 size: offset is rounded down to a page boundary; (offset+nbytes-1) is
24 rounded up to a page boundary.
25 The flags bit-mask argument can include any of the following values:
27 SYNC_FILE_RANGE_WAIT_BEFORE
29 Wait upon write-out of all pages in the specified range that
30 have already been submitted to the device driver for write-out
31 before performing any write.
32 SYNC_FILE_RANGE_WRITE
34 Initiate write-out of all dirty pages in the specified range
35 which are not presently submitted write-out. Note that even
36 this may block if you attempt to write more than request queue
37 size.
38 SYNC_FILE_RANGE_WAIT_AFTER
40 Wait upon write-out of all pages in the range after performing
41 any write.
42 Specifying flags as 0 is permitted, as a no-op.
44 Some details
46 None of these operations write out the file's metadata. Therefore,
47 unless the application is strictly performing overwrites of already-
48 instantiated disk blocks, there are no guarantees that the data will be
49 available after a crash.
50 SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect
52 any I/O errors or ENOSPC conditions and will return these to the call‐
53 er.
54 Useful combinations of the flags bits are:
56 SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE
58 Ensures that all pages in the specified range which were dirty
59 when sync_file_range() was called are placed under write-out.
60 This is a start-write-for-data-integrity operation.
61 SYNC_FILE_RANGE_WRITE
63 Start write-out of all dirty pages in the specified range which
64 are not presently under write-out. This is an asynchronous
65 flush-to-disk operation. This is not suitable for data
66 integrity operations.
67 SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER)
69 Wait for completion of write-out of all pages in the specified
70 range. This can be used after an earlier
71 SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE operation to
72 wait for completion of that operation, and obtain its result.
73 SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE |
75 SYNC_FILE_RANGE_WAIT_AFTER
76 This is a write-for-data-integrity operation that will ensure
77 that all pages in the specified range which were dirty when
78 sync_file_range() was called are committed to disk.
79
81 On success, sync_file_range() returns 0; on failure -1 is returned and
82 errno is set to indicate the error.
83
85 EBADF fd is not a valid file descriptor.
86 EINVAL flags specifies an invalid bit; or offset or nbytes is invalid.
88 EIO I/O error.
90 ENOMEM Out of memory.
92 ENOSPC Out of disk space.
94 ESPIPE fd refers to something other than a regular file, a block
96 device, a directory, or a symbolic link.
97
99 sync_file_range() appeared on Linux in kernel 2.6.17.
100
102 This system call is Linux-specific, and should be avoided in portable
103 programs.
104
106 fdatasync(2), fsync(2), msync(2), sync(2), feature_test_macros(7)
107
109 This page is part of release 3.22 of the Linux man-pages project. A
110 description of the project, and information about reporting bugs, can
111 be found at http://www.kernel.org/doc/man-pages/.
112Linux 2008-05-27 SYNC_FILE_RANGE(2)