diff options
Diffstat (limited to 'fs/sync.c')
| -rw-r--r-- | fs/sync.c | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/fs/sync.c b/fs/sync.c new file mode 100644 index 0000000..8616006 --- /dev/null +++ b/fs/sync.c @@ -0,0 +1,164 @@ +/* + * 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, + 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, + 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); |
