--- /dev/null
+/*
+ * High-level sync()-related operations
+ */
+
+#include <linux/kernel.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/writeback.h>
+#include <linux/syscalls.h>
+#include <linux/linkage.h>
+#include <linux/pagemap.h>
+
+#define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
+ SYNC_FILE_RANGE_WAIT_AFTER)
+
+/*
+ * sys_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.
+ *
+ * The flag bits are:
+ *
+ * SYNC_FILE_RANGE_WAIT_BEFORE: wait upon writeout of all pages in the range
+ * before performing the write.
+ *
+ * SYNC_FILE_RANGE_WRITE: initiate writeout of all those dirty pages in the
+ * range which are not presently under writeback.
+ *
+ * SYNC_FILE_RANGE_WAIT_AFTER: wait upon writeout of all pages in the range
+ * after performing the write.
+ *
+ * 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
+ * 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
+ * are not presently under writeout. This is an asynchronous flush-to-disk
+ * operation. Not suitable for data integrity operations.
+ *
+ * SYNC_FILE_RANGE_WAIT_BEFORE (or SYNC_FILE_RANGE_WAIT_AFTER): wait for
+ * completion of writeout of all pages in the range. This will be used after an
+ * 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:
+ * 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.
+ *
+ *
+ * SYNC_FILE_RANGE_WAIT_BEFORE and SYNC_FILE_RANGE_WAIT_AFTER will detect any
+ * I/O errors or ENOSPC conditions and will return those to the caller, after
+ * clearing the EIO and ENOSPC flags in the address_space.
+ *
+ * It should be noted that none of these operations write out the file's
+ * metadata. So unless the application is strictly performing overwrites of
+ * already-instantiated disk blocks, there are no guarantees here that the data
+ * will be available after a crash.
+ */
+asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes,
+ unsigned int flags)
+{
+ int ret;
+ struct file *file;
+ loff_t endbyte; /* inclusive */
+ int fput_needed;
+ umode_t i_mode;
+
+ ret = -EINVAL;
+ if (flags & ~VALID_FLAGS)
+ goto out;
+
+ endbyte = offset + nbytes;
+
+ if ((s64)offset < 0)
+ goto out;
+ if ((s64)endbyte < 0)
+ goto out;
+ if (endbyte < offset)
+ goto out;
+
+ if (sizeof(pgoff_t) == 4) {
+ if (offset >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
+ /*
+ * The range starts outside a 32 bit machine's
+ * pagecache addressing capabilities. Let it "succeed"
+ */
+ ret = 0;
+ goto out;
+ }
+ if (endbyte >= (0x100000000ULL << PAGE_CACHE_SHIFT)) {
+ /*
+ * Out to EOF
+ */
+ nbytes = 0;
+ }
+ }
+
+ if (nbytes == 0)
+ endbyte = -1;
+ else
+ endbyte--; /* inclusive */
+
+ ret = -EBADF;
+ file = fget_light(fd, &fput_needed);
+ if (!file)
+ goto out;
+
+ i_mode = file->f_dentry->d_inode->i_mode;
+ ret = -ESPIPE;
+ if (!S_ISREG(i_mode) && !S_ISBLK(i_mode) && !S_ISDIR(i_mode) &&
+ !S_ISLNK(i_mode))
+ goto out_put;
+
+ ret = do_sync_file_range(file, offset, endbyte, flags);
+out_put:
+ fput_light(file, fput_needed);
+out:
+ return ret;
+}
+
+/*
+ * `endbyte' is inclusive
+ */
+int do_sync_file_range(struct file *file, loff_t offset, loff_t endbyte,
+ unsigned int flags)
+{
+ int ret;
+ struct address_space *mapping;
+
+ mapping = file->f_mapping;
+ if (!mapping) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = 0;
+ if (flags & SYNC_FILE_RANGE_WAIT_BEFORE) {
+ ret = wait_on_page_writeback_range(mapping,
+ offset >> PAGE_CACHE_SHIFT,
+ endbyte >> PAGE_CACHE_SHIFT);
+ if (ret < 0)
+ goto out;
+ }
+
+ if (flags & SYNC_FILE_RANGE_WRITE) {
+ ret = __filemap_fdatawrite_range(mapping, offset, endbyte,
+ WB_SYNC_NONE);
+ if (ret < 0)
+ goto out;
+ }
+
+ if (flags & SYNC_FILE_RANGE_WAIT_AFTER) {
+ ret = wait_on_page_writeback_range(mapping,
+ offset >> PAGE_CACHE_SHIFT,
+ endbyte >> PAGE_CACHE_SHIFT);
+ }
+out:
+ return ret;
+}
+EXPORT_SYMBOL_GPL(do_sync_file_range);
git://git.onelab.eu / linux-2.6.git / blobdiff