/* fs/fat/nfs.c
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 */

#include <linux/exportfs.h>
#include "fat.h"

struct fat_fid {
	u32 i_gen;
	u32 i_pos_low;
	u16 i_pos_hi;
	u16 parent_i_pos_hi;
	u32 parent_i_pos_low;
	u32 parent_i_gen;
};

#define FAT_FID_SIZE_WITHOUT_PARENT 3
#define FAT_FID_SIZE_WITH_PARENT (sizeof(struct fat_fid)/sizeof(u32))

/**
 * Look up a directory inode given its starting cluster.
 */
static struct inode *fat_dget(struct super_block *sb, int i_logstart)
{
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct hlist_head *head;
	struct msdos_inode_info *i;
	struct inode *inode = NULL;

	head = sbi->dir_hashtable + fat_dir_hash(i_logstart);
	spin_lock(&sbi->dir_hash_lock);
	hlist_for_each_entry(i, head, i_dir_hash) {
		BUG_ON(i->vfs_inode.i_sb != sb);
		if (i->i_logstart != i_logstart)
			continue;
		inode = igrab(&i->vfs_inode);
		if (inode)
			break;
	}
	spin_unlock(&sbi->dir_hash_lock);
	return inode;
}

static struct inode *fat_ilookup(struct super_block *sb, u64 ino, loff_t i_pos)
{
	if (MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO)
		return fat_iget(sb, i_pos);

	else {
		if ((ino < MSDOS_ROOT_INO) || (ino == MSDOS_FSINFO_INO))
			return NULL;
		return ilookup(sb, ino);
	}
}

static struct inode *__fat_nfs_get_inode(struct super_block *sb,
				       u64 ino, u32 generation, loff_t i_pos)
{
	struct inode *inode = fat_ilookup(sb, ino, i_pos);

	if (inode && generation && (inode->i_generation != generation)) {
		iput(inode);
		inode = NULL;
	}
	if (inode == NULL && MSDOS_SB(sb)->options.nfs == FAT_NFS_NOSTALE_RO) {
		struct buffer_head *bh = NULL;
		struct msdos_dir_entry *de ;
		sector_t blocknr;
		int offset;
		fat_get_blknr_offset(MSDOS_SB(sb), i_pos, &blocknr, &offset);
		bh = sb_bread(sb, blocknr);
		if (!bh) {
			fat_msg(sb, KERN_ERR,
				"unable to read block(%llu) for building NFS inode",
				(llu)blocknr);
			return inode;
		}
		de = (struct msdos_dir_entry *)bh->b_data;
		/* If a file is deleted on server and client is not updated
		 * yet, we must not build the inode upon a lookup call.
		 */
		if (IS_FREE(de[offset].name))
			inode = NULL;
		else
			inode = fat_build_inode(sb, &de[offset], i_pos);
		brelse(bh);
	}

	return inode;
}

static struct inode *fat_nfs_get_inode(struct super_block *sb,
				       u64 ino, u32 generation)
{

	return __fat_nfs_get_inode(sb, ino, generation, 0);
}

static int
fat_encode_fh_nostale(struct inode *inode, __u32 *fh, int *lenp,
		      struct inode *parent)
{
	int len = *lenp;
	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
	struct fat_fid *fid = (struct fat_fid *) fh;
	loff_t i_pos;
	int type = FILEID_FAT_WITHOUT_PARENT;

	if (parent) {
		if (len < FAT_FID_SIZE_WITH_PARENT) {
			*lenp = FAT_FID_SIZE_WITH_PARENT;
			return FILEID_INVALID;
		}
	} else {
		if (len < FAT_FID_SIZE_WITHOUT_PARENT) {
			*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
			return FILEID_INVALID;
		}
	}

	i_pos = fat_i_pos_read(sbi, inode);
	*lenp = FAT_FID_SIZE_WITHOUT_PARENT;
	fid->i_gen = inode->i_generation;
	fid->i_pos_low = i_pos & 0xFFFFFFFF;
	fid->i_pos_hi = (i_pos >> 32) & 0xFFFF;
	if (parent) {
		i_pos = fat_i_pos_read(sbi, parent);
		fid->parent_i_pos_hi = (i_pos >> 32) & 0xFFFF;
		fid->parent_i_pos_low = i_pos & 0xFFFFFFFF;
		fid->parent_i_gen = parent->i_generation;
		type = FILEID_FAT_WITH_PARENT;
		*lenp = FAT_FID_SIZE_WITH_PARENT;
	}

	return type;
}

/**
 * Map a NFS file handle to a corresponding dentry.
 * The dentry may or may not be connected to the filesystem root.
 */
static struct dentry *fat_fh_to_dentry(struct super_block *sb, struct fid *fid,
				int fh_len, int fh_type)
{
	return generic_fh_to_dentry(sb, fid, fh_len, fh_type,
				    fat_nfs_get_inode);
}

static struct dentry *fat_fh_to_dentry_nostale(struct super_block *sb,
					       struct fid *fh, int fh_len,
					       int fh_type)
{
	struct inode *inode = NULL;
	struct fat_fid *fid = (struct fat_fid *)fh;
	loff_t i_pos;

	switch (fh_type) {
	case FILEID_FAT_WITHOUT_PARENT:
		if (fh_len < FAT_FID_SIZE_WITHOUT_PARENT)
			return NULL;
		break;
	case FILEID_FAT_WITH_PARENT:
		if (fh_len < FAT_FID_SIZE_WITH_PARENT)
			return NULL;
		break;
	default:
		return NULL;
	}
	i_pos = fid->i_pos_hi;
	i_pos = (i_pos << 32) | (fid->i_pos_low);
	inode = __fat_nfs_get_inode(sb, 0, fid->i_gen, i_pos);

	return d_obtain_alias(inode);
}

/*
 * Find the parent for a file specified by NFS handle.
 * This requires that the handle contain the i_ino of the parent.
 */
static struct dentry *fat_fh_to_parent(struct super_block *sb, struct fid *fid,
				int fh_len, int fh_type)
{
	return generic_fh_to_parent(sb, fid, fh_len, fh_type,
				    fat_nfs_get_inode);
}

static struct dentry *fat_fh_to_parent_nostale(struct super_block *sb,
					       struct fid *fh, int fh_len,
					       int fh_type)
{
	struct inode *inode = NULL;
	struct fat_fid *fid = (struct fat_fid *)fh;
	loff_t i_pos;

	if (fh_len < FAT_FID_SIZE_WITH_PARENT)
		return NULL;

	switch (fh_type) {
	case FILEID_FAT_WITH_PARENT:
		i_pos = fid->parent_i_pos_hi;
		i_pos = (i_pos << 32) | (fid->parent_i_pos_low);
		inode = __fat_nfs_get_inode(sb, 0, fid->parent_i_gen, i_pos);
		break;
	}

	return d_obtain_alias(inode);
}

/*
 * Rebuild the parent for a directory that is not connected
 *  to the filesystem root
 */
static
struct inode *fat_rebuild_parent(struct super_block *sb, int parent_logstart)
{
	int search_clus, clus_to_match;
	struct msdos_dir_entry *de;
	struct inode *parent = NULL;
	struct inode *dummy_grand_parent = NULL;
	struct fat_slot_info sinfo;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	sector_t blknr = fat_clus_to_blknr(sbi, parent_logstart);
	struct buffer_head *parent_bh = sb_bread(sb, blknr);
	if (!parent_bh) {
		fat_msg(sb, KERN_ERR,
			"unable to read cluster of parent directory");
		return NULL;
	}

	de = (struct msdos_dir_entry *) parent_bh->b_data;
	clus_to_match = fat_get_start(sbi, &de[0]);
	search_clus = fat_get_start(sbi, &de[1]);

	dummy_grand_parent = fat_dget(sb, search_clus);
	if (!dummy_grand_parent) {
		dummy_grand_parent = new_inode(sb);
		if (!dummy_grand_parent) {
			brelse(parent_bh);
			return parent;
		}

		dummy_grand_parent->i_ino = iunique(sb, MSDOS_ROOT_INO);
		fat_fill_inode(dummy_grand_parent, &de[1]);
		MSDOS_I(dummy_grand_parent)->i_pos = -1;
	}

	if (!fat_scan_logstart(dummy_grand_parent, clus_to_match, &sinfo))
		parent = fat_build_inode(sb, sinfo.de, sinfo.i_pos);

	brelse(parent_bh);
	iput(dummy_grand_parent);

	return parent;
}

/*
 * Find the parent for a directory that is not currently connected to
 * the filesystem root.
 *
 * On entry, the caller holds d_inode(child_dir)->i_mutex.
 */
static struct dentry *fat_get_parent(struct dentry *child_dir)
{
	struct super_block *sb = child_dir->d_sb;
	struct buffer_head *bh = NULL;
	struct msdos_dir_entry *de;
	struct inode *parent_inode = NULL;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);

	if (!fat_get_dotdot_entry(d_inode(child_dir), &bh, &de)) {
		int parent_logstart = fat_get_start(sbi, de);
		parent_inode = fat_dget(sb, parent_logstart);
		if (!parent_inode && sbi->options.nfs == FAT_NFS_NOSTALE_RO)
			parent_inode = fat_rebuild_parent(sb, parent_logstart);
	}
	brelse(bh);

	return d_obtain_alias(parent_inode);
}

const struct export_operations fat_export_ops = {
	.fh_to_dentry   = fat_fh_to_dentry,
	.fh_to_parent   = fat_fh_to_parent,
	.get_parent     = fat_get_parent,
};

const struct export_operations fat_export_ops_nostale = {
	.encode_fh      = fat_encode_fh_nostale,
	.fh_to_dentry   = fat_fh_to_dentry_nostale,
	.fh_to_parent   = fat_fh_to_parent_nostale,
	.get_parent     = fat_get_parent,
};
 by adding a NULL pointer
check and a WARN_ON_ONCE() to avoid the oops that would then generally
make the machine unresponsive.

Other callers of i915_gem_object_to_ggtt() seem to also check for the
returned pointer being NULL and warn about it, so this clearly has
happened before in other places.

[ Reported it originally to the i915 developers on Jan 8, applying the
  ugly workaround on my own now after triggering the problem for the
  second time with no feedback.

  This is likely to be the same bug reported as

     https://bugs.freedesktop.org/show_bug.cgi?id=98829
     https://bugs.freedesktop.org/show_bug.cgi?id=99134

  which has a patch for the underlying problem, but it hasn't gotten to
  me, so I'm applying the workaround. ]

Cc: Daniel Vetter &lt;daniel.vetter@intel.com&gt;
Cc: Jani Nikula &lt;jani.nikula@linux.intel.com&gt;
Cc: Ville Syrjälä &lt;ville.syrjala@linux.intel.com&gt;
Cc: Chris Wilson &lt;chris@chris-wilson.co.uk&gt;
Cc: Maarten Lankhorst &lt;maarten.lankhorst@linux.intel.com&gt;
Cc: Tvrtko Ursulin &lt;tvrtko.ursulin@intel.com&gt;
Cc: Imre Deak &lt;imre.deak@intel.com&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?h=nds-private-remove&amp;id=39cb2c9a316e77f6dfba96c543e55b6672d5a37e'>Diffstat</a> (limited to 'sound/pci/ctxfi/ctvmem.h')</div><table summary='diffstat' class='diffstat'>