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![Theodore Ts'o](/assets/img/avatar_default.png)
Previously, the no-op "mount -o mount /dev/xxx" operation when the file system is already mounted read-write causes an implied, unconditional syncfs(). This seems pretty stupid, and it's certainly documented or guaraunteed to do this, nor is it particularly useful, except in the case where the file system was mounted rw and is getting remounted read-only. However, it's possible that there might be some file systems that are actually depending on this behavior. In most file systems, it's probably fine to only call sync_filesystem() when transitioning from read-write to read-only, and there are some file systems where this is not needed at all (for example, for a pseudo-filesystem or something like romfs). Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: linux-fsdevel@vger.kernel.org Cc: Christoph Hellwig <hch@infradead.org> Cc: Artem Bityutskiy <dedekind1@gmail.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Evgeniy Dushistov <dushistov@mail.ru> Cc: Jan Kara <jack@suse.cz> Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> Cc: Anders Larsen <al@alarsen.net> Cc: Phillip Lougher <phillip@squashfs.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> Cc: Petr Vandrovec <petr@vandrovec.name> Cc: xfs@oss.sgi.com Cc: linux-btrfs@vger.kernel.org Cc: linux-cifs@vger.kernel.org Cc: samba-technical@lists.samba.org Cc: codalist@coda.cs.cmu.edu Cc: linux-ext4@vger.kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net Cc: fuse-devel@lists.sourceforge.net Cc: cluster-devel@redhat.com Cc: linux-mtd@lists.infradead.org Cc: jfs-discussion@lists.sourceforge.net Cc: linux-nfs@vger.kernel.org Cc: linux-nilfs@vger.kernel.org Cc: linux-ntfs-dev@lists.sourceforge.net Cc: ocfs2-devel@oss.oracle.com Cc: reiserfs-devel@vger.kernel.org
426 lines
11 KiB
C
426 lines
11 KiB
C
/*
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* QNX4 file system, Linux implementation.
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*
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* Version : 0.2.1
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*
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* Using parts of the xiafs filesystem.
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*
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* History :
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*
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* 01-06-1998 by Richard Frowijn : first release.
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* 20-06-1998 by Frank Denis : Linux 2.1.99+ support, boot signature, misc.
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* 30-06-1998 by Frank Denis : first step to write inodes.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/highuid.h>
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#include <linux/pagemap.h>
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#include <linux/buffer_head.h>
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#include <linux/writeback.h>
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#include <linux/statfs.h>
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#include "qnx4.h"
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#define QNX4_VERSION 4
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#define QNX4_BMNAME ".bitmap"
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static const struct super_operations qnx4_sops;
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static struct inode *qnx4_alloc_inode(struct super_block *sb);
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static void qnx4_destroy_inode(struct inode *inode);
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static int qnx4_remount(struct super_block *sb, int *flags, char *data);
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static int qnx4_statfs(struct dentry *, struct kstatfs *);
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static const struct super_operations qnx4_sops =
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{
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.alloc_inode = qnx4_alloc_inode,
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.destroy_inode = qnx4_destroy_inode,
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.statfs = qnx4_statfs,
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.remount_fs = qnx4_remount,
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};
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static int qnx4_remount(struct super_block *sb, int *flags, char *data)
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{
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struct qnx4_sb_info *qs;
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sync_filesystem(sb);
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qs = qnx4_sb(sb);
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qs->Version = QNX4_VERSION;
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*flags |= MS_RDONLY;
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return 0;
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}
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static int qnx4_get_block( struct inode *inode, sector_t iblock, struct buffer_head *bh, int create )
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{
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unsigned long phys;
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QNX4DEBUG((KERN_INFO "qnx4: qnx4_get_block inode=[%ld] iblock=[%ld]\n",inode->i_ino,iblock));
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phys = qnx4_block_map( inode, iblock );
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if ( phys ) {
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// logical block is before EOF
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map_bh(bh, inode->i_sb, phys);
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}
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return 0;
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}
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static inline u32 try_extent(qnx4_xtnt_t *extent, u32 *offset)
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{
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u32 size = le32_to_cpu(extent->xtnt_size);
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if (*offset < size)
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return le32_to_cpu(extent->xtnt_blk) + *offset - 1;
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*offset -= size;
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return 0;
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}
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unsigned long qnx4_block_map( struct inode *inode, long iblock )
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{
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int ix;
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long i_xblk;
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struct buffer_head *bh = NULL;
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struct qnx4_xblk *xblk = NULL;
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struct qnx4_inode_entry *qnx4_inode = qnx4_raw_inode(inode);
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u16 nxtnt = le16_to_cpu(qnx4_inode->di_num_xtnts);
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u32 offset = iblock;
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u32 block = try_extent(&qnx4_inode->di_first_xtnt, &offset);
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if (block) {
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// iblock is in the first extent. This is easy.
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} else {
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// iblock is beyond first extent. We have to follow the extent chain.
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i_xblk = le32_to_cpu(qnx4_inode->di_xblk);
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ix = 0;
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while ( --nxtnt > 0 ) {
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if ( ix == 0 ) {
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// read next xtnt block.
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bh = sb_bread(inode->i_sb, i_xblk - 1);
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if ( !bh ) {
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QNX4DEBUG((KERN_ERR "qnx4: I/O error reading xtnt block [%ld])\n", i_xblk - 1));
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return -EIO;
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}
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xblk = (struct qnx4_xblk*)bh->b_data;
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if ( memcmp( xblk->xblk_signature, "IamXblk", 7 ) ) {
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QNX4DEBUG((KERN_ERR "qnx4: block at %ld is not a valid xtnt\n", qnx4_inode->i_xblk));
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return -EIO;
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}
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}
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block = try_extent(&xblk->xblk_xtnts[ix], &offset);
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if (block) {
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// got it!
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break;
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}
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if ( ++ix >= xblk->xblk_num_xtnts ) {
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i_xblk = le32_to_cpu(xblk->xblk_next_xblk);
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ix = 0;
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brelse( bh );
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bh = NULL;
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}
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}
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if ( bh )
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brelse( bh );
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}
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QNX4DEBUG((KERN_INFO "qnx4: mapping block %ld of inode %ld = %ld\n",iblock,inode->i_ino,block));
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return block;
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}
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static int qnx4_statfs(struct dentry *dentry, struct kstatfs *buf)
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{
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struct super_block *sb = dentry->d_sb;
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u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
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buf->f_type = sb->s_magic;
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buf->f_bsize = sb->s_blocksize;
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buf->f_blocks = le32_to_cpu(qnx4_sb(sb)->BitMap->di_size) * 8;
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buf->f_bfree = qnx4_count_free_blocks(sb);
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buf->f_bavail = buf->f_bfree;
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buf->f_namelen = QNX4_NAME_MAX;
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buf->f_fsid.val[0] = (u32)id;
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buf->f_fsid.val[1] = (u32)(id >> 32);
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return 0;
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}
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/*
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* Check the root directory of the filesystem to make sure
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* it really _is_ a qnx4 filesystem, and to check the size
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* of the directory entry.
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*/
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static const char *qnx4_checkroot(struct super_block *sb,
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struct qnx4_super_block *s)
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{
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struct buffer_head *bh;
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struct qnx4_inode_entry *rootdir;
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int rd, rl;
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int i, j;
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if (s->RootDir.di_fname[0] != '/' || s->RootDir.di_fname[1] != '\0')
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return "no qnx4 filesystem (no root dir).";
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QNX4DEBUG((KERN_NOTICE "QNX4 filesystem found on dev %s.\n", sb->s_id));
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rd = le32_to_cpu(s->RootDir.di_first_xtnt.xtnt_blk) - 1;
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rl = le32_to_cpu(s->RootDir.di_first_xtnt.xtnt_size);
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for (j = 0; j < rl; j++) {
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bh = sb_bread(sb, rd + j); /* root dir, first block */
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if (bh == NULL)
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return "unable to read root entry.";
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rootdir = (struct qnx4_inode_entry *) bh->b_data;
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for (i = 0; i < QNX4_INODES_PER_BLOCK; i++, rootdir++) {
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QNX4DEBUG((KERN_INFO "rootdir entry found : [%s]\n", rootdir->di_fname));
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if (strcmp(rootdir->di_fname, QNX4_BMNAME) != 0)
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continue;
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qnx4_sb(sb)->BitMap = kmemdup(rootdir,
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sizeof(struct qnx4_inode_entry),
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GFP_KERNEL);
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brelse(bh);
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if (!qnx4_sb(sb)->BitMap)
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return "not enough memory for bitmap inode";
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/* keep bitmap inode known */
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return NULL;
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}
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brelse(bh);
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}
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return "bitmap file not found.";
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}
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static int qnx4_fill_super(struct super_block *s, void *data, int silent)
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{
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struct buffer_head *bh;
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struct inode *root;
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const char *errmsg;
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struct qnx4_sb_info *qs;
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qs = kzalloc(sizeof(struct qnx4_sb_info), GFP_KERNEL);
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if (!qs)
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return -ENOMEM;
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s->s_fs_info = qs;
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sb_set_blocksize(s, QNX4_BLOCK_SIZE);
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s->s_op = &qnx4_sops;
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s->s_magic = QNX4_SUPER_MAGIC;
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s->s_flags |= MS_RDONLY; /* Yup, read-only yet */
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/* Check the superblock signature. Since the qnx4 code is
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dangerous, we should leave as quickly as possible
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if we don't belong here... */
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bh = sb_bread(s, 1);
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if (!bh) {
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printk(KERN_ERR "qnx4: unable to read the superblock\n");
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return -EINVAL;
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}
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/* check before allocating dentries, inodes, .. */
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errmsg = qnx4_checkroot(s, (struct qnx4_super_block *) bh->b_data);
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brelse(bh);
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if (errmsg != NULL) {
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if (!silent)
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printk(KERN_ERR "qnx4: %s\n", errmsg);
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return -EINVAL;
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}
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/* does root not have inode number QNX4_ROOT_INO ?? */
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root = qnx4_iget(s, QNX4_ROOT_INO * QNX4_INODES_PER_BLOCK);
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if (IS_ERR(root)) {
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printk(KERN_ERR "qnx4: get inode failed\n");
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return PTR_ERR(root);
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}
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s->s_root = d_make_root(root);
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if (s->s_root == NULL)
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return -ENOMEM;
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return 0;
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}
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static void qnx4_kill_sb(struct super_block *sb)
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{
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struct qnx4_sb_info *qs = qnx4_sb(sb);
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kill_block_super(sb);
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if (qs) {
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kfree(qs->BitMap);
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kfree(qs);
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}
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}
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static int qnx4_readpage(struct file *file, struct page *page)
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{
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return block_read_full_page(page,qnx4_get_block);
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}
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static sector_t qnx4_bmap(struct address_space *mapping, sector_t block)
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{
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return generic_block_bmap(mapping,block,qnx4_get_block);
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}
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static const struct address_space_operations qnx4_aops = {
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.readpage = qnx4_readpage,
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.bmap = qnx4_bmap
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};
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struct inode *qnx4_iget(struct super_block *sb, unsigned long ino)
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{
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struct buffer_head *bh;
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struct qnx4_inode_entry *raw_inode;
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int block;
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struct qnx4_inode_entry *qnx4_inode;
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struct inode *inode;
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inode = iget_locked(sb, ino);
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if (!inode)
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return ERR_PTR(-ENOMEM);
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if (!(inode->i_state & I_NEW))
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return inode;
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qnx4_inode = qnx4_raw_inode(inode);
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inode->i_mode = 0;
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QNX4DEBUG((KERN_INFO "reading inode : [%d]\n", ino));
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if (!ino) {
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printk(KERN_ERR "qnx4: bad inode number on dev %s: %lu is "
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"out of range\n",
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sb->s_id, ino);
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iget_failed(inode);
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return ERR_PTR(-EIO);
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}
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block = ino / QNX4_INODES_PER_BLOCK;
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if (!(bh = sb_bread(sb, block))) {
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printk(KERN_ERR "qnx4: major problem: unable to read inode from dev "
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"%s\n", sb->s_id);
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iget_failed(inode);
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return ERR_PTR(-EIO);
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}
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raw_inode = ((struct qnx4_inode_entry *) bh->b_data) +
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(ino % QNX4_INODES_PER_BLOCK);
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inode->i_mode = le16_to_cpu(raw_inode->di_mode);
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i_uid_write(inode, (uid_t)le16_to_cpu(raw_inode->di_uid));
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i_gid_write(inode, (gid_t)le16_to_cpu(raw_inode->di_gid));
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set_nlink(inode, le16_to_cpu(raw_inode->di_nlink));
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inode->i_size = le32_to_cpu(raw_inode->di_size);
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inode->i_mtime.tv_sec = le32_to_cpu(raw_inode->di_mtime);
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inode->i_mtime.tv_nsec = 0;
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inode->i_atime.tv_sec = le32_to_cpu(raw_inode->di_atime);
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inode->i_atime.tv_nsec = 0;
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inode->i_ctime.tv_sec = le32_to_cpu(raw_inode->di_ctime);
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inode->i_ctime.tv_nsec = 0;
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inode->i_blocks = le32_to_cpu(raw_inode->di_first_xtnt.xtnt_size);
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memcpy(qnx4_inode, raw_inode, QNX4_DIR_ENTRY_SIZE);
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if (S_ISREG(inode->i_mode)) {
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inode->i_fop = &generic_ro_fops;
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inode->i_mapping->a_ops = &qnx4_aops;
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qnx4_i(inode)->mmu_private = inode->i_size;
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} else if (S_ISDIR(inode->i_mode)) {
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inode->i_op = &qnx4_dir_inode_operations;
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inode->i_fop = &qnx4_dir_operations;
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} else if (S_ISLNK(inode->i_mode)) {
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inode->i_op = &page_symlink_inode_operations;
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inode->i_mapping->a_ops = &qnx4_aops;
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qnx4_i(inode)->mmu_private = inode->i_size;
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} else {
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printk(KERN_ERR "qnx4: bad inode %lu on dev %s\n",
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ino, sb->s_id);
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iget_failed(inode);
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brelse(bh);
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return ERR_PTR(-EIO);
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}
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brelse(bh);
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unlock_new_inode(inode);
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return inode;
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}
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static struct kmem_cache *qnx4_inode_cachep;
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static struct inode *qnx4_alloc_inode(struct super_block *sb)
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{
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struct qnx4_inode_info *ei;
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ei = kmem_cache_alloc(qnx4_inode_cachep, GFP_KERNEL);
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if (!ei)
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return NULL;
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return &ei->vfs_inode;
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}
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static void qnx4_i_callback(struct rcu_head *head)
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{
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struct inode *inode = container_of(head, struct inode, i_rcu);
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kmem_cache_free(qnx4_inode_cachep, qnx4_i(inode));
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}
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static void qnx4_destroy_inode(struct inode *inode)
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{
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call_rcu(&inode->i_rcu, qnx4_i_callback);
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}
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static void init_once(void *foo)
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{
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struct qnx4_inode_info *ei = (struct qnx4_inode_info *) foo;
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inode_init_once(&ei->vfs_inode);
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}
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static int init_inodecache(void)
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{
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qnx4_inode_cachep = kmem_cache_create("qnx4_inode_cache",
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sizeof(struct qnx4_inode_info),
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0, (SLAB_RECLAIM_ACCOUNT|
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SLAB_MEM_SPREAD),
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init_once);
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if (qnx4_inode_cachep == NULL)
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return -ENOMEM;
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return 0;
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}
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static void destroy_inodecache(void)
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{
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/*
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* Make sure all delayed rcu free inodes are flushed before we
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* destroy cache.
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*/
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rcu_barrier();
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kmem_cache_destroy(qnx4_inode_cachep);
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}
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static struct dentry *qnx4_mount(struct file_system_type *fs_type,
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int flags, const char *dev_name, void *data)
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{
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return mount_bdev(fs_type, flags, dev_name, data, qnx4_fill_super);
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}
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static struct file_system_type qnx4_fs_type = {
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.owner = THIS_MODULE,
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.name = "qnx4",
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.mount = qnx4_mount,
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.kill_sb = qnx4_kill_sb,
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.fs_flags = FS_REQUIRES_DEV,
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};
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MODULE_ALIAS_FS("qnx4");
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static int __init init_qnx4_fs(void)
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{
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int err;
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err = init_inodecache();
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if (err)
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return err;
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err = register_filesystem(&qnx4_fs_type);
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if (err) {
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destroy_inodecache();
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return err;
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}
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printk(KERN_INFO "QNX4 filesystem 0.2.3 registered.\n");
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return 0;
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}
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static void __exit exit_qnx4_fs(void)
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{
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unregister_filesystem(&qnx4_fs_type);
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destroy_inodecache();
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}
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module_init(init_qnx4_fs)
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module_exit(exit_qnx4_fs)
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MODULE_LICENSE("GPL");
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