fs/jfs/jfs_mount.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  *   Copyright (C) International Business Machines Corp., 2000-2004
  */

 /*
  * Module: jfs_mount.c
  *
  * note: file system in transition to aggregate/fileset:
  *
  * file system mount is interpreted as the mount of aggregate,
  * if not already mounted, and mount of the single/only fileset in
  * the aggregate;
  *
  * a file system/aggregate is represented by an internal inode
  * (aka mount inode) initialized with aggregate superblock;
  * each vfs represents a fileset, and points to its "fileset inode
  * allocation map inode" (aka fileset inode):
  * (an aggregate itself is structured recursively as a filset:
  * an internal vfs is constructed and points to its "fileset inode
  * allocation map inode" (aka aggregate inode) where each inode
  * represents a fileset inode) so that inode number is mapped to
  * on-disk inode in uniform way at both aggregate and fileset level;
  *
  * each vnode/inode of a fileset is linked to its vfs (to facilitate
  * per fileset inode operations, e.g., unmount of a fileset, etc.);
  * each inode points to the mount inode (to facilitate access to
  * per aggregate information, e.g., block size, etc.) as well as
  * its file set inode.
  *
  *   aggregate
  *   ipmnt
  *   mntvfs -> fileset ipimap+ -> aggregate ipbmap -> aggregate ipaimap;
  *             fileset vfs     -> vp(1) <-> ... <-> vp(n) <->vproot;
  */

 #include <linux/fs.h>
 #include <linux/buffer_head.h>
 #include <linux/blkdev.h>
 #include <linux/log2.h>

 #include "jfs_incore.h"
 #include "jfs_filsys.h"
 #include "jfs_superblock.h"
 #include "jfs_dmap.h"
 #include "jfs_imap.h"
 #include "jfs_metapage.h"
 #include "jfs_debug.h"


 /*
  * forward references
  */
 static int chkSuper(struct super_block *);
 static int logMOUNT(struct super_block *sb);

 /*
  * NAME:	jfs_mount(sb)
  *
  * FUNCTION:	vfs_mount()
  *
  * PARAMETER:	sb	- super block
  *
  * RETURN:	-EBUSY	- device already mounted or open for write
  *		-EBUSY	- cvrdvp already mounted;
  *		-EBUSY	- mount table full
  *		-ENOTDIR- cvrdvp not directory on a device mount
  *		-ENXIO	- device open failure
  */
 int jfs_mount(struct super_block *sb)
 {
 	int rc = 0;		/* Return code */
 	struct jfs_sb_info *sbi = JFS_SBI(sb);
 	struct inode *ipaimap = NULL;
 	struct inode *ipaimap2 = NULL;
 	struct inode *ipimap = NULL;
 	struct inode *ipbmap = NULL;

 	/*
 	 * read/validate superblock
 	 * (initialize mount inode from the superblock)
 	 */
 	if ((rc = chkSuper(sb))) {
 		goto out;
 	}

 	ipaimap = diReadSpecial(sb, AGGREGATE_I, 0);
 	if (ipaimap == NULL) {
 		jfs_err("jfs_mount: Failed to read AGGREGATE_I");
 		rc = -EIO;
 		goto out;
 	}
 	sbi->ipaimap = ipaimap;

 	jfs_info("jfs_mount: ipaimap:0x%p", ipaimap);

 	/*
 	 * initialize aggregate inode allocation map
 	 */
 	if ((rc = diMount(ipaimap))) {
 		jfs_err("jfs_mount: diMount(ipaimap) failed w/rc = %d", rc);
 		goto err_ipaimap;
 	}

 	/*
 	 * open aggregate block allocation map
 	 */
 	ipbmap = diReadSpecial(sb, BMAP_I, 0);
 	if (ipbmap == NULL) {
 		rc = -EIO;
 		goto err_umount_ipaimap;
 	}

 	jfs_info("jfs_mount: ipbmap:0x%p", ipbmap);

 	sbi->ipbmap = ipbmap;

 	/*
 	 * initialize aggregate block allocation map
 	 */
 	if ((rc = dbMount(ipbmap))) {
 		jfs_err("jfs_mount: dbMount failed w/rc = %d", rc);
 		goto err_ipbmap;
 	}

 	/*
 	 * open the secondary aggregate inode allocation map
 	 *
 	 * This is a duplicate of the aggregate inode allocation map.
 	 *
 	 * hand craft a vfs in the same fashion as we did to read ipaimap.
 	 * By adding INOSPEREXT (32) to the inode number, we are telling
 	 * diReadSpecial that we are reading from the secondary aggregate
 	 * inode table.  This also creates a unique entry in the inode hash
 	 * table.
 	 */
 	if ((sbi->mntflag & JFS_BAD_SAIT) == 0) {
 		ipaimap2 = diReadSpecial(sb, AGGREGATE_I, 1);
 		if (!ipaimap2) {
 			jfs_err("jfs_mount: Failed to read AGGREGATE_I");
 			rc = -EIO;
 			goto err_umount_ipbmap;
 		}
 		sbi->ipaimap2 = ipaimap2;

 		jfs_info("jfs_mount: ipaimap2:0x%p", ipaimap2);

 		/*
 		 * initialize secondary aggregate inode allocation map
 		 */
 		if ((rc = diMount(ipaimap2))) {
 			jfs_err("jfs_mount: diMount(ipaimap2) failed, rc = %d",
 				rc);
 			goto err_ipaimap2;
 		}
 	} else
 		/* Secondary aggregate inode table is not valid */
 		sbi->ipaimap2 = NULL;

 	/*
 	 *	mount (the only/single) fileset
 	 */
 	/*
 	 * open fileset inode allocation map (aka fileset inode)
 	 */
 	ipimap = diReadSpecial(sb, FILESYSTEM_I, 0);
 	if (ipimap == NULL) {
 		jfs_err("jfs_mount: Failed to read FILESYSTEM_I");
 		/* open fileset secondary inode allocation map */
 		rc = -EIO;
 		goto err_umount_ipaimap2;
 	}
 	jfs_info("jfs_mount: ipimap:0x%p", ipimap);

 	/* map further access of per fileset inodes by the fileset inode */
 	sbi->ipimap = ipimap;

 	/* initialize fileset inode allocation map */
 	if ((rc = diMount(ipimap))) {
 		jfs_err("jfs_mount: diMount failed w/rc = %d", rc);
 		goto err_ipimap;
 	}

 	return rc;

 	/*
 	 *	unwind on error
 	 */
 err_ipimap:
 	/* close fileset inode allocation map inode */
 	diFreeSpecial(ipimap);
 err_umount_ipaimap2:
 	/* close secondary aggregate inode allocation map */
 	if (ipaimap2)
 		diUnmount(ipaimap2, 1);
 err_ipaimap2:
 	/* close aggregate inodes */
 	if (ipaimap2)
 		diFreeSpecial(ipaimap2);
 err_umount_ipbmap:	/* close aggregate block allocation map */
 	dbUnmount(ipbmap, 1);
 err_ipbmap:		/* close aggregate inodes */
 	diFreeSpecial(ipbmap);
 err_umount_ipaimap:	/* close aggregate inode allocation map */
 	diUnmount(ipaimap, 1);
 err_ipaimap:		/* close aggregate inodes */
 	diFreeSpecial(ipaimap);
 out:
 	if (rc)
 		jfs_err("Mount JFS Failure: %d", rc);

 	return rc;
 }

 /*
  * NAME:	jfs_mount_rw(sb, remount)
  *
  * FUNCTION:	Completes read-write mount, or remounts read-only volume
  *		as read-write
  */
 int jfs_mount_rw(struct super_block *sb, int remount)
 {
 	struct jfs_sb_info *sbi = JFS_SBI(sb);
 	int rc;

 	/*
 	 * If we are re-mounting a previously read-only volume, we want to
 	 * re-read the inode and block maps, since fsck.jfs may have updated
 	 * them.
 	 */
 	if (remount) {
 		if (chkSuper(sb) || (sbi->state != FM_CLEAN))
 			return -EINVAL;

 		truncate_inode_pages(sbi->ipimap->i_mapping, 0);
 		truncate_inode_pages(sbi->ipbmap->i_mapping, 0);

 		IWRITE_LOCK(sbi->ipimap, RDWRLOCK_IMAP);
 		diUnmount(sbi->ipimap, 1);
 		if ((rc = diMount(sbi->ipimap))) {
 			IWRITE_UNLOCK(sbi->ipimap);
 			jfs_err("jfs_mount_rw: diMount failed!");
 			return rc;
 		}
 		IWRITE_UNLOCK(sbi->ipimap);

 		dbUnmount(sbi->ipbmap, 1);
 		if ((rc = dbMount(sbi->ipbmap))) {
 			jfs_err("jfs_mount_rw: dbMount failed!");
 			return rc;
 		}
 	}

 	/*
 	 * open/initialize log
 	 */
 	if ((rc = lmLogOpen(sb)))
 		return rc;

 	/*
 	 * update file system superblock;
 	 */
 	if ((rc = updateSuper(sb, FM_MOUNT))) {
 		jfs_err("jfs_mount: updateSuper failed w/rc = %d", rc);
 		lmLogClose(sb);
 		return rc;
 	}

 	/*
 	 * write MOUNT log record of the file system
 	 */
 	logMOUNT(sb);

 	return rc;
 }

 /*
  *	chkSuper()
  *
  * validate the superblock of the file system to be mounted and
  * get the file system parameters.
  *
  * returns
  *	0 with fragsize set if check successful
  *	error code if not successful
  */
 static int chkSuper(struct super_block *sb)
 {
 	int rc = 0;
 	struct jfs_sb_info *sbi = JFS_SBI(sb);
 	struct jfs_superblock *j_sb;
 	struct buffer_head *bh;
 	int AIM_bytesize, AIT_bytesize;
 	int expected_AIM_bytesize, expected_AIT_bytesize;
 	s64 AIM_byte_addr, AIT_byte_addr, fsckwsp_addr;
 	s64 byte_addr_diff0, byte_addr_diff1;
 	s32 bsize;

 	if ((rc = readSuper(sb, &bh)))
 		return rc;
 	j_sb = (struct jfs_superblock *)bh->b_data;

 	/*
 	 * validate superblock
 	 */
 	/* validate fs signature */
 	if (strncmp(j_sb->s_magic, JFS_MAGIC, 4) ||
 	    le32_to_cpu(j_sb->s_version) > JFS_VERSION) {
 		rc = -EINVAL;
 		goto out;
 	}

 	bsize = le32_to_cpu(j_sb->s_bsize);
 	if (bsize != PSIZE) {
 		jfs_err("Only 4K block size supported!");
 		rc = -EINVAL;
 		goto out;
 	}

 	jfs_info("superblock: flag:0x%08x state:0x%08x size:0x%Lx",
 		 le32_to_cpu(j_sb->s_flag), le32_to_cpu(j_sb->s_state),
 		 (unsigned long long) le64_to_cpu(j_sb->s_size));

 	/* validate the descriptors for Secondary AIM and AIT */
 	if ((j_sb->s_flag & cpu_to_le32(JFS_BAD_SAIT)) !=
 	    cpu_to_le32(JFS_BAD_SAIT)) {
 		expected_AIM_bytesize = 2 * PSIZE;
 		AIM_bytesize = lengthPXD(&(j_sb->s_aim2)) * bsize;
 		expected_AIT_bytesize = 4 * PSIZE;
 		AIT_bytesize = lengthPXD(&(j_sb->s_ait2)) * bsize;
 		AIM_byte_addr = addressPXD(&(j_sb->s_aim2)) * bsize;
 		AIT_byte_addr = addressPXD(&(j_sb->s_ait2)) * bsize;
 		byte_addr_diff0 = AIT_byte_addr - AIM_byte_addr;
 		fsckwsp_addr = addressPXD(&(j_sb->s_fsckpxd)) * bsize;
 		byte_addr_diff1 = fsckwsp_addr - AIT_byte_addr;
 		if ((AIM_bytesize != expected_AIM_bytesize) ||
 		    (AIT_bytesize != expected_AIT_bytesize) ||
 		    (byte_addr_diff0 != AIM_bytesize) ||
 		    (byte_addr_diff1 <= AIT_bytesize))
 			j_sb->s_flag |= cpu_to_le32(JFS_BAD_SAIT);
 	}

 	if ((j_sb->s_flag & cpu_to_le32(JFS_GROUPCOMMIT)) !=
 	    cpu_to_le32(JFS_GROUPCOMMIT))
 		j_sb->s_flag |= cpu_to_le32(JFS_GROUPCOMMIT);

 	/* validate fs state */
 	if (j_sb->s_state != cpu_to_le32(FM_CLEAN) &&
 	    !sb_rdonly(sb)) {
 		jfs_err("jfs_mount: Mount Failure: File System Dirty.");
 		rc = -EINVAL;
 		goto out;
 	}

 	sbi->state = le32_to_cpu(j_sb->s_state);
 	sbi->mntflag = le32_to_cpu(j_sb->s_flag);

 	/*
 	 * JFS always does I/O by 4K pages.  Don't tell the buffer cache
 	 * that we use anything else (leave s_blocksize alone).
 	 */
 	sbi->bsize = bsize;
 	sbi->l2bsize = le16_to_cpu(j_sb->s_l2bsize);

 	/* check some fields for possible corruption */
 	if (sbi->l2bsize != ilog2((u32)bsize) ||
 	    j_sb->pad != 0 ||
 	    le32_to_cpu(j_sb->s_state) > FM_STATE_MAX) {
 		rc = -EINVAL;
 		jfs_err("jfs_mount: Mount Failure: superblock is corrupt!");
 		goto out;
 	}

 	/*
 	 * For now, ignore s_pbsize, l2bfactor.  All I/O going through buffer
 	 * cache.
 	 */
 	sbi->nbperpage = PSIZE >> sbi->l2bsize;
 	sbi->l2nbperpage = L2PSIZE - sbi->l2bsize;
 	sbi->l2niperblk = sbi->l2bsize - L2DISIZE;
 	if (sbi->mntflag & JFS_INLINELOG)
 		sbi->logpxd = j_sb->s_logpxd;
 	else {
 		sbi->logdev = new_decode_dev(le32_to_cpu(j_sb->s_logdev));
 		uuid_copy(&sbi->uuid, &j_sb->s_uuid);
 		uuid_copy(&sbi->loguuid, &j_sb->s_loguuid);
 	}
 	sbi->fsckpxd = j_sb->s_fsckpxd;
 	sbi->ait2 = j_sb->s_ait2;

       out:
 	brelse(bh);
 	return rc;
 }


 /*
  *	updateSuper()
  *
  * update synchronously superblock if it is mounted read-write.
  */
 int updateSuper(struct super_block *sb, uint state)
 {
 	struct jfs_superblock *j_sb;
 	struct jfs_sb_info *sbi = JFS_SBI(sb);
 	struct buffer_head *bh;
 	int rc;

 	if (sbi->flag & JFS_NOINTEGRITY) {
 		if (state == FM_DIRTY) {
 			sbi->p_state = state;
 			return 0;
 		} else if (state == FM_MOUNT) {
 			sbi->p_state = sbi->state;
 			state = FM_DIRTY;
 		} else if (state == FM_CLEAN) {
 			state = sbi->p_state;
 		} else
 			jfs_err("updateSuper: bad state");
 	} else if (sbi->state == FM_DIRTY)
 		return 0;

 	if ((rc = readSuper(sb, &bh)))
 		return rc;

 	j_sb = (struct jfs_superblock *)bh->b_data;

 	j_sb->s_state = cpu_to_le32(state);
 	sbi->state = state;

 	if (state == FM_MOUNT) {
 		/* record log's dev_t and mount serial number */
 		j_sb->s_logdev = cpu_to_le32(new_encode_dev(sbi->log->bdev->bd_dev));
 		j_sb->s_logserial = cpu_to_le32(sbi->log->serial);
 	} else if (state == FM_CLEAN) {
 		/*
 		 * If this volume is shared with OS/2, OS/2 will need to
 		 * recalculate DASD usage, since we don't deal with it.
 		 */
 		if (j_sb->s_flag & cpu_to_le32(JFS_DASD_ENABLED))
 			j_sb->s_flag |= cpu_to_le32(JFS_DASD_PRIME);
 	}

 	mark_buffer_dirty(bh);
 	sync_dirty_buffer(bh);
 	brelse(bh);

 	return 0;
 }


 /*
  *	readSuper()
  *
  * read superblock by raw sector address
  */
 int readSuper(struct super_block *sb, struct buffer_head **bpp)
 {
 	/* read in primary superblock */
 	*bpp = sb_bread(sb, SUPER1_OFF >> sb->s_blocksize_bits);
 	if (*bpp)
 		return 0;

 	/* read in secondary/replicated superblock */
 	*bpp = sb_bread(sb, SUPER2_OFF >> sb->s_blocksize_bits);
 	if (*bpp)
 		return 0;

 	return -EIO;
 }


 /*
  *	logMOUNT()
  *
  * function: write a MOUNT log record for file system.
  *
  * MOUNT record keeps logredo() from processing log records
  * for this file system past this point in log.
  * it is harmless if mount fails.
  *
  * note: MOUNT record is at aggregate level, not at fileset level,
  * since log records of previous mounts of a fileset
  * (e.g., AFTER record of extent allocation) have to be processed
  * to update block allocation map at aggregate level.
  */
 static int logMOUNT(struct super_block *sb)
 {
 	struct jfs_log *log = JFS_SBI(sb)->log;
 	struct lrd lrd;

 	lrd.logtid = 0;
 	lrd.backchain = 0;
 	lrd.type = cpu_to_le16(LOG_MOUNT);
 	lrd.length = 0;
 	lrd.aggregate = cpu_to_le32(new_encode_dev(sb->s_bdev->bd_dev));
 	lmLog(log, NULL, &lrd, NULL);

 	return 0;
 }
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Copyright (C) International Business Machines Corp., 2000-2004
	*/

	/*
	* Module: jfs_mount.c
	*
	* note: file system in transition to aggregate/fileset:
	*
	* file system mount is interpreted as the mount of aggregate,
	* if not already mounted, and mount of the single/only fileset in
	* the aggregate;
	*
	* a file system/aggregate is represented by an internal inode
	* (aka mount inode) initialized with aggregate superblock;
	* each vfs represents a fileset, and points to its "fileset inode
	* allocation map inode" (aka fileset inode):
	* (an aggregate itself is structured recursively as a filset:
	* an internal vfs is constructed and points to its "fileset inode
	* allocation map inode" (aka aggregate inode) where each inode
	* represents a fileset inode) so that inode number is mapped to
	* on-disk inode in uniform way at both aggregate and fileset level;
	*
	* each vnode/inode of a fileset is linked to its vfs (to facilitate
	* per fileset inode operations, e.g., unmount of a fileset, etc.);
	* each inode points to the mount inode (to facilitate access to
	* per aggregate information, e.g., block size, etc.) as well as
	* its file set inode.
	*
	* aggregate
	* ipmnt
	* mntvfs -> fileset ipimap+ -> aggregate ipbmap -> aggregate ipaimap;
	* fileset vfs -> vp(1) <-> ... <-> vp(n) <->vproot;
	*/

	#include <linux/fs.h>
	#include <linux/buffer_head.h>
	#include <linux/blkdev.h>
	#include <linux/log2.h>

	#include "jfs_incore.h"
	#include "jfs_filsys.h"
	#include "jfs_superblock.h"
	#include "jfs_dmap.h"
	#include "jfs_imap.h"
	#include "jfs_metapage.h"
	#include "jfs_debug.h"


	/*
	* forward references
	*/
	static int chkSuper(struct super_block *);
	static int logMOUNT(struct super_block *sb);

	/*
	* NAME: jfs_mount(sb)
	*
	* FUNCTION: vfs_mount()
	*
	* PARAMETER: sb - super block
	*
	* RETURN: -EBUSY - device already mounted or open for write
	* -EBUSY - cvrdvp already mounted;
	* -EBUSY - mount table full
	* -ENOTDIR- cvrdvp not directory on a device mount
	* -ENXIO - device open failure
	*/
	int jfs_mount(struct super_block *sb)
	{
	int rc = 0; /* Return code */
	struct jfs_sb_info *sbi = JFS_SBI(sb);
	struct inode *ipaimap = NULL;
	struct inode *ipaimap2 = NULL;
	struct inode *ipimap = NULL;
	struct inode *ipbmap = NULL;

	/*
	* read/validate superblock
	* (initialize mount inode from the superblock)
	*/
	if ((rc = chkSuper(sb))) {
	goto out;
	}

	ipaimap = diReadSpecial(sb, AGGREGATE_I, 0);
	if (ipaimap == NULL) {
	jfs_err("jfs_mount: Failed to read AGGREGATE_I");
	rc = -EIO;
	goto out;
	}
	sbi->ipaimap = ipaimap;

	jfs_info("jfs_mount: ipaimap:0x%p", ipaimap);

	/*
	* initialize aggregate inode allocation map
	*/
	if ((rc = diMount(ipaimap))) {
	jfs_err("jfs_mount: diMount(ipaimap) failed w/rc = %d", rc);
	goto err_ipaimap;
	}

	/*
	* open aggregate block allocation map
	*/
	ipbmap = diReadSpecial(sb, BMAP_I, 0);
	if (ipbmap == NULL) {
	rc = -EIO;
	goto err_umount_ipaimap;
	}

	jfs_info("jfs_mount: ipbmap:0x%p", ipbmap);

	sbi->ipbmap = ipbmap;

	/*
	* initialize aggregate block allocation map
	*/
	if ((rc = dbMount(ipbmap))) {
	jfs_err("jfs_mount: dbMount failed w/rc = %d", rc);
	goto err_ipbmap;
	}

	/*
	* open the secondary aggregate inode allocation map
	*
	* This is a duplicate of the aggregate inode allocation map.
	*
	* hand craft a vfs in the same fashion as we did to read ipaimap.
	* By adding INOSPEREXT (32) to the inode number, we are telling
	* diReadSpecial that we are reading from the secondary aggregate
	* inode table. This also creates a unique entry in the inode hash
	* table.
	*/
	if ((sbi->mntflag & JFS_BAD_SAIT) == 0) {
	ipaimap2 = diReadSpecial(sb, AGGREGATE_I, 1);
	if (!ipaimap2) {
	jfs_err("jfs_mount: Failed to read AGGREGATE_I");
	rc = -EIO;
	goto err_umount_ipbmap;
	}
	sbi->ipaimap2 = ipaimap2;

	jfs_info("jfs_mount: ipaimap2:0x%p", ipaimap2);

	/*
	* initialize secondary aggregate inode allocation map
	*/
	if ((rc = diMount(ipaimap2))) {
	jfs_err("jfs_mount: diMount(ipaimap2) failed, rc = %d",
	rc);
	goto err_ipaimap2;
	}
	} else
	/* Secondary aggregate inode table is not valid */
	sbi->ipaimap2 = NULL;

	/*
	* mount (the only/single) fileset
	*/
	/*
	* open fileset inode allocation map (aka fileset inode)
	*/
	ipimap = diReadSpecial(sb, FILESYSTEM_I, 0);
	if (ipimap == NULL) {
	jfs_err("jfs_mount: Failed to read FILESYSTEM_I");
	/* open fileset secondary inode allocation map */
	rc = -EIO;
	goto err_umount_ipaimap2;
	}
	jfs_info("jfs_mount: ipimap:0x%p", ipimap);

	/* map further access of per fileset inodes by the fileset inode */
	sbi->ipimap = ipimap;

	/* initialize fileset inode allocation map */
	if ((rc = diMount(ipimap))) {
	jfs_err("jfs_mount: diMount failed w/rc = %d", rc);
	goto err_ipimap;
	}

	return rc;

	/*
	* unwind on error
	*/
	err_ipimap:
	/* close fileset inode allocation map inode */
	diFreeSpecial(ipimap);
	err_umount_ipaimap2:
	/* close secondary aggregate inode allocation map */
	if (ipaimap2)
	diUnmount(ipaimap2, 1);
	err_ipaimap2:
	/* close aggregate inodes */
	if (ipaimap2)
	diFreeSpecial(ipaimap2);
	err_umount_ipbmap: /* close aggregate block allocation map */
	dbUnmount(ipbmap, 1);
	err_ipbmap: /* close aggregate inodes */
	diFreeSpecial(ipbmap);
	err_umount_ipaimap: /* close aggregate inode allocation map */
	diUnmount(ipaimap, 1);
	err_ipaimap: /* close aggregate inodes */
	diFreeSpecial(ipaimap);
	out:
	if (rc)
	jfs_err("Mount JFS Failure: %d", rc);

	return rc;
	}

	/*
	* NAME: jfs_mount_rw(sb, remount)
	*
	* FUNCTION: Completes read-write mount, or remounts read-only volume
	* as read-write
	*/
	int jfs_mount_rw(struct super_block *sb, int remount)
	{
	struct jfs_sb_info *sbi = JFS_SBI(sb);
	int rc;

	/*
	* If we are re-mounting a previously read-only volume, we want to
	* re-read the inode and block maps, since fsck.jfs may have updated
	* them.
	*/
	if (remount) {
	if (chkSuper(sb) \|\| (sbi->state != FM_CLEAN))
	return -EINVAL;

	truncate_inode_pages(sbi->ipimap->i_mapping, 0);
	truncate_inode_pages(sbi->ipbmap->i_mapping, 0);

	IWRITE_LOCK(sbi->ipimap, RDWRLOCK_IMAP);
	diUnmount(sbi->ipimap, 1);
	if ((rc = diMount(sbi->ipimap))) {
	IWRITE_UNLOCK(sbi->ipimap);
	jfs_err("jfs_mount_rw: diMount failed!");
	return rc;
	}
	IWRITE_UNLOCK(sbi->ipimap);

	dbUnmount(sbi->ipbmap, 1);
	if ((rc = dbMount(sbi->ipbmap))) {
	jfs_err("jfs_mount_rw: dbMount failed!");
	return rc;
	}
	}

	/*
	* open/initialize log
	*/
	if ((rc = lmLogOpen(sb)))
	return rc;

	/*
	* update file system superblock;
	*/
	if ((rc = updateSuper(sb, FM_MOUNT))) {
	jfs_err("jfs_mount: updateSuper failed w/rc = %d", rc);
	lmLogClose(sb);
	return rc;
	}

	/*
	* write MOUNT log record of the file system
	*/
	logMOUNT(sb);

	return rc;
	}

	/*
	* chkSuper()
	*
	* validate the superblock of the file system to be mounted and
	* get the file system parameters.
	*
	* returns
	* 0 with fragsize set if check successful
	* error code if not successful
	*/
	static int chkSuper(struct super_block *sb)
	{
	int rc = 0;
	struct jfs_sb_info *sbi = JFS_SBI(sb);
	struct jfs_superblock *j_sb;
	struct buffer_head *bh;
	int AIM_bytesize, AIT_bytesize;
	int expected_AIM_bytesize, expected_AIT_bytesize;
	s64 AIM_byte_addr, AIT_byte_addr, fsckwsp_addr;
	s64 byte_addr_diff0, byte_addr_diff1;
	s32 bsize;

	if ((rc = readSuper(sb, &bh)))
	return rc;
	j_sb = (struct jfs_superblock *)bh->b_data;

	/*
	* validate superblock
	*/
	/* validate fs signature */
	if (strncmp(j_sb->s_magic, JFS_MAGIC, 4) \|\|
	le32_to_cpu(j_sb->s_version) > JFS_VERSION) {
	rc = -EINVAL;
	goto out;
	}

	bsize = le32_to_cpu(j_sb->s_bsize);
	if (bsize != PSIZE) {
	jfs_err("Only 4K block size supported!");
	rc = -EINVAL;
	goto out;
	}

	jfs_info("superblock: flag:0x%08x state:0x%08x size:0x%Lx",
	le32_to_cpu(j_sb->s_flag), le32_to_cpu(j_sb->s_state),
	(unsigned long long) le64_to_cpu(j_sb->s_size));

	/* validate the descriptors for Secondary AIM and AIT */
	if ((j_sb->s_flag & cpu_to_le32(JFS_BAD_SAIT)) !=
	cpu_to_le32(JFS_BAD_SAIT)) {
	expected_AIM_bytesize = 2 * PSIZE;
	AIM_bytesize = lengthPXD(&(j_sb->s_aim2)) * bsize;
	expected_AIT_bytesize = 4 * PSIZE;
	AIT_bytesize = lengthPXD(&(j_sb->s_ait2)) * bsize;
	AIM_byte_addr = addressPXD(&(j_sb->s_aim2)) * bsize;
	AIT_byte_addr = addressPXD(&(j_sb->s_ait2)) * bsize;
	byte_addr_diff0 = AIT_byte_addr - AIM_byte_addr;
	fsckwsp_addr = addressPXD(&(j_sb->s_fsckpxd)) * bsize;
	byte_addr_diff1 = fsckwsp_addr - AIT_byte_addr;
	if ((AIM_bytesize != expected_AIM_bytesize) \|\|
	(AIT_bytesize != expected_AIT_bytesize) \|\|
	(byte_addr_diff0 != AIM_bytesize) \|\|
	(byte_addr_diff1 <= AIT_bytesize))
	j_sb->s_flag \|= cpu_to_le32(JFS_BAD_SAIT);
	}

	if ((j_sb->s_flag & cpu_to_le32(JFS_GROUPCOMMIT)) !=
	cpu_to_le32(JFS_GROUPCOMMIT))
	j_sb->s_flag \|= cpu_to_le32(JFS_GROUPCOMMIT);

	/* validate fs state */
	if (j_sb->s_state != cpu_to_le32(FM_CLEAN) &&
	!sb_rdonly(sb)) {
	jfs_err("jfs_mount: Mount Failure: File System Dirty.");
	rc = -EINVAL;
	goto out;
	}

	sbi->state = le32_to_cpu(j_sb->s_state);
	sbi->mntflag = le32_to_cpu(j_sb->s_flag);

	/*
	* JFS always does I/O by 4K pages. Don't tell the buffer cache
	* that we use anything else (leave s_blocksize alone).
	*/
	sbi->bsize = bsize;
	sbi->l2bsize = le16_to_cpu(j_sb->s_l2bsize);

	/* check some fields for possible corruption */
	if (sbi->l2bsize != ilog2((u32)bsize) \|\|
	j_sb->pad != 0 \|\|
	le32_to_cpu(j_sb->s_state) > FM_STATE_MAX) {
	rc = -EINVAL;
	jfs_err("jfs_mount: Mount Failure: superblock is corrupt!");
	goto out;
	}

	/*
	* For now, ignore s_pbsize, l2bfactor. All I/O going through buffer
	* cache.
	*/
	sbi->nbperpage = PSIZE >> sbi->l2bsize;
	sbi->l2nbperpage = L2PSIZE - sbi->l2bsize;
	sbi->l2niperblk = sbi->l2bsize - L2DISIZE;
	if (sbi->mntflag & JFS_INLINELOG)
	sbi->logpxd = j_sb->s_logpxd;
	else {
	sbi->logdev = new_decode_dev(le32_to_cpu(j_sb->s_logdev));
	uuid_copy(&sbi->uuid, &j_sb->s_uuid);
	uuid_copy(&sbi->loguuid, &j_sb->s_loguuid);
	}
	sbi->fsckpxd = j_sb->s_fsckpxd;
	sbi->ait2 = j_sb->s_ait2;

	out:
	brelse(bh);
	return rc;
	}


	/*
	* updateSuper()
	*
	* update synchronously superblock if it is mounted read-write.
	*/
	int updateSuper(struct super_block *sb, uint state)
	{
	struct jfs_superblock *j_sb;
	struct jfs_sb_info *sbi = JFS_SBI(sb);
	struct buffer_head *bh;
	int rc;

	if (sbi->flag & JFS_NOINTEGRITY) {
	if (state == FM_DIRTY) {
	sbi->p_state = state;
	return 0;
	} else if (state == FM_MOUNT) {
	sbi->p_state = sbi->state;
	state = FM_DIRTY;
	} else if (state == FM_CLEAN) {
	state = sbi->p_state;
	} else
	jfs_err("updateSuper: bad state");
	} else if (sbi->state == FM_DIRTY)
	return 0;

	if ((rc = readSuper(sb, &bh)))
	return rc;

	j_sb = (struct jfs_superblock *)bh->b_data;

	j_sb->s_state = cpu_to_le32(state);
	sbi->state = state;

	if (state == FM_MOUNT) {
	/* record log's dev_t and mount serial number */
	j_sb->s_logdev = cpu_to_le32(new_encode_dev(sbi->log->bdev->bd_dev));
	j_sb->s_logserial = cpu_to_le32(sbi->log->serial);
	} else if (state == FM_CLEAN) {
	/*
	* If this volume is shared with OS/2, OS/2 will need to
	* recalculate DASD usage, since we don't deal with it.
	*/
	if (j_sb->s_flag & cpu_to_le32(JFS_DASD_ENABLED))
	j_sb->s_flag \|= cpu_to_le32(JFS_DASD_PRIME);
	}

	mark_buffer_dirty(bh);
	sync_dirty_buffer(bh);
	brelse(bh);

	return 0;
	}


	/*
	* readSuper()
	*
	* read superblock by raw sector address
	*/
	int readSuper(struct super_block sb, struct buffer_head *bpp)
	{
	/* read in primary superblock */
	*bpp = sb_bread(sb, SUPER1_OFF >> sb->s_blocksize_bits);
	if (*bpp)
	return 0;

	/* read in secondary/replicated superblock */
	*bpp = sb_bread(sb, SUPER2_OFF >> sb->s_blocksize_bits);
	if (*bpp)
	return 0;

	return -EIO;
	}


	/*
	* logMOUNT()
	*
	* function: write a MOUNT log record for file system.
	*
	* MOUNT record keeps logredo() from processing log records
	* for this file system past this point in log.
	* it is harmless if mount fails.
	*
	* note: MOUNT record is at aggregate level, not at fileset level,
	* since log records of previous mounts of a fileset
	* (e.g., AFTER record of extent allocation) have to be processed
	* to update block allocation map at aggregate level.
	*/
	static int logMOUNT(struct super_block *sb)
	{
	struct jfs_log *log = JFS_SBI(sb)->log;
	struct lrd lrd;

	lrd.logtid = 0;
	lrd.backchain = 0;
	lrd.type = cpu_to_le16(LOG_MOUNT);
	lrd.length = 0;
	lrd.aggregate = cpu_to_le32(new_encode_dev(sb->s_bdev->bd_dev));
	lmLog(log, NULL, &lrd, NULL);

	return 0;
	}