This system call is by design completely unsuitable for any data integrity operations. Make that very clear in the manpage. Signed-off-by: Christoph Hellwig <hch@xxxxxx> Index: man-pages/man2/sync_file_range.2 =================================================================== --- man-pages.orig/man2/sync_file_range.2 2009-08-27 14:51:51.373360594 -0300 +++ man-pages/man2/sync_file_range.2 2009-08-27 14:57:35.213854927 -0300 @@ -80,11 +80,22 @@ after performing any write. Specifying .I flags as 0 is permitted, as a no-op. -.SS Some details -None of these operations write out the file's metadata. +.SS WARNING +This system call is extremly dangerous and should not be used in portable +programs. None of these operations write out the file's metadata. Therefore, unless the application is strictly performing overwrites of -already-instantiated disk blocks, -there are no guarantees that the data will be available after a crash. +already-instantiated disk blocks, there are no guarantees that the data will +be available after a crash. There is no user interface to know if a +write is purely an overwrite. On filesystem using copy on write semantics +like +.IR btrfs +an over write of existing allocated blocks is impossible. Writing into +pre-allocated space many filesystems also require calls into the block +allocator which this system call does not sync out to disk. +This system call does not flush disk write caches and thus does not provide +any data integrity on systems with volatile disk write caches. + +.SS Some details .B SYNC_FILE_RANGE_WAIT_BEFORE and -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
