diff options
| -rw-r--r-- | fs/read_write.c | 45 | ||||
| -rw-r--r-- | include/linux/fs.h | 2 |
2 files changed, 47 insertions, 0 deletions
diff --git a/fs/read_write.c b/fs/read_write.c index b07e48cd81d1..fb519e55c8e8 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -181,6 +181,51 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence, EXPORT_SYMBOL(generic_file_llseek_size); /** + * generic_llseek_cookie - versioned llseek implementation + * @file: file structure to seek on + * @offset: file offset to seek to + * @whence: type of seek + * @cookie: cookie to update + * + * See generic_file_llseek for a general description and locking assumptions. + * + * In contrast to generic_file_llseek, this function also resets a + * specified cookie to indicate a seek took place. + */ +loff_t generic_llseek_cookie(struct file *file, loff_t offset, int whence, + u64 *cookie) +{ + struct inode *inode = file->f_mapping->host; + loff_t maxsize = inode->i_sb->s_maxbytes; + loff_t eof = i_size_read(inode); + int ret; + + if (WARN_ON_ONCE(!cookie)) + return -EINVAL; + + /* + * Require that this is only used for directories that guarantee + * synchronization between readdir and seek so that an update to + * @cookie is correctly synchronized with concurrent readdir. + */ + if (WARN_ON_ONCE(!(file->f_mode & FMODE_ATOMIC_POS))) + return -EINVAL; + + ret = must_set_pos(file, &offset, whence, eof); + if (ret < 0) + return ret; + if (ret == 0) + return offset; + + /* No need to hold f_lock because we know that f_pos_lock is held. */ + if (whence == SEEK_CUR) + return vfs_setpos_cookie(file, file->f_pos + offset, maxsize, cookie); + + return vfs_setpos_cookie(file, offset, maxsize, cookie); +} +EXPORT_SYMBOL(generic_llseek_cookie); + +/** * generic_file_llseek - generic llseek implementation for regular files * @file: file structure to seek on * @offset: file offset to seek to diff --git a/include/linux/fs.h b/include/linux/fs.h index 58c91a52cad1..3e6b3c1afb31 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -3202,6 +3202,8 @@ extern loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize); extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence); extern loff_t generic_file_llseek_size(struct file *file, loff_t offset, int whence, loff_t maxsize, loff_t eof); +loff_t generic_llseek_cookie(struct file *file, loff_t offset, int whence, + u64 *cookie); extern loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t size); extern loff_t no_seek_end_llseek_size(struct file *, loff_t, int, loff_t); |