From: Eric Sandeen Subject: [PATCH] vfs: allow custom EOF in generic_file_llseek code Date: Fri, 27 Apr 2012 11:21:04 -0500 Message-ID: <4F9AC770.8080004@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: ext4 development , Andreas Dilger , Bernd Schubert To: "linux-fsdevel@vger.kernel.org" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:10602 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759610Ab2D0QVL (ORCPT ); Fri, 27 Apr 2012 12:21:11 -0400 Sender: linux-ext4-owner@vger.kernel.org List-ID: For ext3/4 htree directories, using the vfs llseek function with SEEK_END goes to i_size like for any other file, but in reality we want the maximum possible hash value. Recent changes in ext4 have cut & pasted generic_file_llseek() back into fs/ext4/dir.c, but replicating this core code seems like a bad idea, especially since the copy has already diverged from the vfs. This patch implements a version of generic_file_llseek which can accept both a custom maximum offset, and a custom EOF position. With this in place, ext4_dir_llseek can pass in the appropriate maximum hash position for both maxsize and eof, and get what it wants. As far as I know, this does not fix any bugs - nfs in the kernel doesn't use SEEK_END, and I don't know of any user who does. But some ext4 folks seem keen on doing the right thing here, and I can't really argue. (Patch also fixes up some comments slightly) Signed-off-by: Eric Sandeen --- diff --git a/fs/read_write.c b/fs/read_write.c index ffc99d2..ecd1828 100644 --- a/fs/read_write.c +++ b/fs/read_write.c @@ -51,14 +51,15 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, } /** - * generic_file_llseek_size - generic llseek implementation for regular files + * generic_file_llseek_size_eof - generic llseek implementation for regular files * @file: file structure to seek on * @offset: file offset to seek to * @origin: type of seek - * @size: max size of file system + * @size: 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 - * file size. + * 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) @@ -66,14 +67,14 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, * read/writes behave like SEEK_SET against seeks. */ loff_t -generic_file_llseek_size(struct file *file, loff_t offset, int origin, - loff_t maxsize) +generic_file_llseek_size_eof(struct file *file, loff_t offset, int origin, + loff_t maxsize, loff_t eof) { struct inode *inode = file->f_mapping->host; switch (origin) { case SEEK_END: - offset += i_size_read(inode); + offset += eof; break; case SEEK_CUR: /* @@ -99,7 +100,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int origin, * 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 (offset >= i_size_read(inode)) + if (offset >= eof) return -ENXIO; break; case SEEK_HOLE: @@ -107,14 +108,35 @@ generic_file_llseek_size(struct file *file, loff_t offset, int origin, * 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 (offset >= i_size_read(inode)) + if (offset >= eof) return -ENXIO; - offset = i_size_read(inode); + offset = eof; break; } return lseek_execute(file, inode, offset, maxsize); } +EXPORT_SYMBOL(generic_file_llseek_size_eof); + +/** + * generic_file_llseek_size - generic llseek implementation for regular files + * @file: file structure to seek on + * @offset: file offset to seek to + * @origin: type of seek + * @size: max size of this file in file system + * + * This is a variant of generic_file_llseek that allows passing in a custom + * maximum file size. + */ +loff_t +generic_file_llseek_size(struct file *file, loff_t offset, int origin, + loff_t maxsize) +{ + struct inode *inode = file->f_mapping->host; + + return generic_file_llseek_size_eof(file, offset, origin, maxsize, + i_size_read(inode)); +} EXPORT_SYMBOL(generic_file_llseek_size); /** @@ -131,8 +153,9 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int origin) { struct inode *inode = file->f_mapping->host; - return generic_file_llseek_size(file, offset, origin, - inode->i_sb->s_maxbytes); + return generic_file_llseek_size_eof(file, offset, origin, + inode->i_sb->s_maxbytes, + i_size_read(inode)); } EXPORT_SYMBOL(generic_file_llseek); diff --git a/include/linux/fs.h b/include/linux/fs.h index 8de6755..a6ae7a4 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2402,6 +2402,8 @@ extern loff_t no_llseek(struct file *file, loff_t offset, int origin); extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin); extern loff_t generic_file_llseek_size(struct file *file, loff_t offset, int origin, loff_t maxsize); +extern loff_t generic_file_llseek_size_eof(struct file *file, loff_t offset, + int origin, loff_t maxsize, loff_t eof); extern int generic_file_open(struct inode * inode, struct file * filp); extern int nonseekable_open(struct inode * inode, struct file * filp);