2 * High-level sync()-related operations
5 #include <linux/kernel.h>
6 #include <linux/file.h>
8 #include <linux/module.h>
9 #include <linux/writeback.h>
10 #include <linux/syscalls.h>
11 #include <linux/linkage.h>
12 #include <linux/pagemap.h>
14 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
15 SYNC_FILE_RANGE_WAIT_AFTER)
18 * sys_sync_file_range() permits finely controlled syncing over a segment of
19 * a file in the range offset .. (offset+nbytes-1) inclusive. If nbytes is
20 * zero then sys_sync_file_range() will operate from offset out to EOF.
24 * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
25 * before performing the write.
27 * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
28 * range which are not presently under writeback.
30 * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
31 * after performing the write.
33 * Useful combinations of the flag bits are:
35 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE: ensures that all pages
36 * in the range which were dirty on entry to sys_sync_file_range() are placed
37 * under writeout. This is a start-write-for-data-integrity operation.
39 * SYNC_FILE_RANGE_WRITE: start writeout of all dirty pages in the range which
40 * are not presently under writeout. This is an asynchronous flush-to-disk
41 * operation. Not suitable for data integrity operations.
43 * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
44 * completion of writeout of all pages in the range. This will be used after an
45 * earlier SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE operation to wait
46 * for that operation to complete and to return the result.
48 * SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE|SYNC_FILE_RANGE_WAIT_AFTER:
49 * a traditional sync() operation. This is a write-for-data-integrity operation
50 * which will ensure that all pages in the range which were dirty on entry to
51 * sys_sync_file_range() are committed to disk.
54 * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
55 * I/O errors or ENOSPC conditions and will return those to the caller, after
56 * clearing the EIO and ENOSPC flags in the address_space.
58 * It should be noted that none of these operations write out the file's
59 * metadata. So unless the application is strictly performing overwrites of
60 * already-instantiated disk blocks, there are no guarantees here that the data
61 * will be available after a crash.
63 asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
68 loff_t endbyte; /* inclusive */
73 if (flags & ~VALID_FLAGS)
76 endbyte = offset + nbytes;
85 if (sizeof(pgoff_t) == 4) {
86 if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
88 * The range starts outside a 32 bit machine's
89 * pagecache addressing capabilities. Let it "succeed"
94 if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
105 endbyte--; /* inclusive */
108 file = fget_light(fd, &fput_needed);
112 i_mode = file->f_dentry->d_inode->i_mode;
114 if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
118 ret = do_sync_file_range(file, offset, endbyte, flags);
120 fput_light(file, fput_needed);
126 * `endbyte' is inclusive
128 int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
132 struct address_space *mapping;
134 mapping = file->f_mapping;
141 if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
142 ret = wait_on_page_writeback_range(mapping,
143 offset >> PAGE_CACHE_SHIFT,
144 endbyte >> PAGE_CACHE_SHIFT);
149 if (flags & SYNC_FILE_RANGE_WRITE) {
150 ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
156 if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
157 ret = wait_on_page_writeback_range(mapping,
158 offset >> PAGE_CACHE_SHIFT,
159 endbyte >> PAGE_CACHE_SHIFT);
164 EXPORT_SYMBOL_GPL(do_sync_file_range);