diff options
Diffstat (limited to 'fs/read_write.c')
| -rw-r--r-- | fs/read_write.c | 173 |
1 files changed, 133 insertions, 40 deletions
diff --git a/fs/read_write.c b/fs/read_write.c index 90e283b31ca1..070a7c33b9dd 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -36,22 +36,24 @@ EXPORT_SYMBOL(generic_ro_fops); static inline bool unsigned_offsets(struct file *file) { - return file->f_mode & FMODE_UNSIGNED_OFFSET; + return file->f_op->fop_flags & FOP_UNSIGNED_OFFSET; } /** - * vfs_setpos - update the file offset for lseek + * vfs_setpos_cookie - update the file offset for lseek and reset cookie * @file: file structure in question * @offset: file offset to seek to * @maxsize: maximum file size + * @cookie: cookie to reset * - * This is a low-level filesystem helper for updating the file offset to - * the value specified by @offset if the given offset is valid and it is - * not equal to the current file offset. + * Update the file offset to the value specified by @offset if the given + * offset is valid and it is not equal to the current file offset and + * reset the specified cookie to indicate that a seek happened. * * Return the specified offset on success and -EINVAL on invalid offset. */ -loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize) +static loff_t vfs_setpos_cookie(struct file *file, loff_t offset, + loff_t maxsize, u64 *cookie) { if (offset < 0 && !unsigned_offsets(file)) return -EINVAL; @@ -60,35 +62,48 @@ loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize) if (offset != file->f_pos) { file->f_pos = offset; - file->f_version = 0; + if (cookie) + *cookie = 0; } return offset; } -EXPORT_SYMBOL(vfs_setpos); /** - * generic_file_llseek_size - generic llseek implementation for regular files - * @file: file structure to seek on + * vfs_setpos - update the file offset for lseek + * @file: file structure in question * @offset: file offset to seek to - * @whence: type of seek - * @maxsize: max size of this file in file system - * @eof: offset used for SEEK_END position + * @maxsize: maximum file size * - * This is a variant of generic_file_llseek that allows passing in a custom - * maximum file size and a custom EOF position, for e.g. hashed directories + * This is a low-level filesystem helper for updating the file offset to + * the value specified by @offset if the given offset is valid and it is + * not equal to the current file offset. * - * Synchronization: - * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms) - * SEEK_CUR is synchronized against other SEEK_CURs, but not read/writes. - * read/writes behave like SEEK_SET against seeks. + * Return the specified offset on success and -EINVAL on invalid offset. */ -loff_t -generic_file_llseek_size(struct file *file, loff_t offset, int whence, - loff_t maxsize, loff_t eof) +loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize) +{ + return vfs_setpos_cookie(file, offset, maxsize, NULL); +} +EXPORT_SYMBOL(vfs_setpos); + +/** + * must_set_pos - check whether f_pos has to be updated + * @file: file to seek on + * @offset: offset to use + * @whence: type of seek operation + * @eof: end of file + * + * Check whether f_pos needs to be updated and update @offset according + * to @whence. + * + * Return: 0 if f_pos doesn't need to be updated, 1 if f_pos has to be + * updated, and negative error code on failure. + */ +static int must_set_pos(struct file *file, loff_t *offset, int whence, loff_t eof) { switch (whence) { case SEEK_END: - offset += eof; + *offset += eof; break; case SEEK_CUR: /* @@ -97,23 +112,17 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence, * f_pos value back to the file because a concurrent read(), * write() or lseek() might have altered it */ - if (offset == 0) - return file->f_pos; - /* - * f_lock protects against read/modify/write race with other - * SEEK_CURs. Note that parallel writes and reads behave - * like SEEK_SET. - */ - spin_lock(&file->f_lock); - offset = vfs_setpos(file, file->f_pos + offset, maxsize); - spin_unlock(&file->f_lock); - return offset; + if (*offset == 0) { + *offset = file->f_pos; + return 0; + } + break; case SEEK_DATA: /* * In the generic case the entire file is data, so as long as * offset isn't at the end of the file then the offset is data. */ - if ((unsigned long long)offset >= eof) + if ((unsigned long long)*offset >= eof) return -ENXIO; break; case SEEK_HOLE: @@ -121,17 +130,103 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence, * There is a virtual hole at the end of the file, so as long as * offset isn't i_size or larger, return i_size. */ - if ((unsigned long long)offset >= eof) + if ((unsigned long long)*offset >= eof) return -ENXIO; - offset = eof; + *offset = eof; break; } + return 1; +} + +/** + * generic_file_llseek_size - generic llseek implementation for regular files + * @file: file structure to seek on + * @offset: file offset to seek to + * @whence: type of seek + * @maxsize: max size of this file in file system + * @eof: offset used for SEEK_END position + * + * This is a variant of generic_file_llseek that allows passing in a custom + * maximum file size and a custom EOF position, for e.g. hashed directories + * + * Synchronization: + * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms) + * SEEK_CUR is synchronized against other SEEK_CURs, but not read/writes. + * read/writes behave like SEEK_SET against seeks. + */ +loff_t +generic_file_llseek_size(struct file *file, loff_t offset, int whence, + loff_t maxsize, loff_t eof) +{ + int ret; + + ret = must_set_pos(file, &offset, whence, eof); + if (ret < 0) + return ret; + if (ret == 0) + return offset; + + if (whence == SEEK_CUR) { + /* + * f_lock protects against read/modify/write race with + * other SEEK_CURs. Note that parallel writes and reads + * behave like SEEK_SET. + */ + guard(spinlock)(&file->f_lock); + return vfs_setpos(file, file->f_pos + offset, maxsize); + } + return vfs_setpos(file, offset, maxsize); } 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 @@ -270,10 +365,8 @@ loff_t default_llseek(struct file *file, loff_t offset, int whence) } retval = -EINVAL; if (offset >= 0 || unsigned_offsets(file)) { - if (offset != file->f_pos) { + if (offset != file->f_pos) file->f_pos = offset; - file->f_version = 0; - } retval = offset; } out: |