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/*-
* Copyright (c) 2003-2004 Tim J. Robbins.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/*
* Compress 64-bit file numbers into temporary, unique 32-bit file numbers.
* This is needed because the algorithm we use to calculate these numbers
* generates 64-bit quantities, but struct dirent's d_fileno member and
* struct vnodeattr's va_fileid member only have space for 32 bits.
*
* 32-bit file numbers are generated sequentially, and stored in a
* red-black tree, indexed on 64-bit file number. The mappings do not
* persist across reboots (or unmounts); anything that relies on this
* (e.g. NFS) will not work correctly. This scheme consumes 32 bytes
* of kernel memory per file (on i386), and it may be possible for a user
* to cause a panic by creating millions of tiny files.
*
* As an optimization, we split the file number space between statically
* allocated and dynamically allocated. File numbers less than
* FILENO_FIRST_DYN are left unchanged and do not have any tree nodes
* allocated to them.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/mutex.h>
#include <fs/msdosfs/bpb.h>
#include <fs/msdosfs/direntry.h>
#include <fs/msdosfs/msdosfsmount.h>
static MALLOC_DEFINE(M_MSDOSFSFILENO, "msdosfs_fileno", "MSDOSFS fileno mapping node");
static struct mtx fileno_mtx;
MTX_SYSINIT(fileno, &fileno_mtx, "MSDOSFS fileno", MTX_DEF);
RB_PROTOTYPE(msdosfs_filenotree, msdosfs_fileno, mf_tree,
msdosfs_fileno_compare)
static int msdosfs_fileno_compare(struct msdosfs_fileno *,
struct msdosfs_fileno *);
#define FILENO_FIRST_DYN 0xf0000000
/* Initialize file number mapping structures. */
void
msdosfs_fileno_init(mp)
struct mount *mp;
{
struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
RB_INIT(&pmp->pm_filenos);
pmp->pm_nfileno = FILENO_FIRST_DYN;
if (pmp->pm_HugeSectors > 0xffffffff /
(pmp->pm_BytesPerSec / sizeof(struct direntry)) + 1)
pmp->pm_flags |= MSDOSFS_LARGEFS;
}
/* Free 32-bit file number generation structures. */
void
msdosfs_fileno_free(mp)
struct mount *mp;
{
struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
struct msdosfs_fileno *mf, *next;
for (mf = RB_MIN(msdosfs_filenotree, &pmp->pm_filenos); mf != NULL;
mf = next) {
next = RB_NEXT(msdosfs_filenotree, &pmp->pm_filenos, mf);
RB_REMOVE(msdosfs_filenotree, &pmp->pm_filenos, mf);
free(mf, M_MSDOSFSFILENO);
}
}
/* Map a 64-bit file number into a 32-bit one. */
uint32_t
msdosfs_fileno_map(mp, fileno)
struct mount *mp;
uint64_t fileno;
{
struct msdosfsmount *pmp = VFSTOMSDOSFS(mp);
struct msdosfs_fileno key, *mf, *tmf;
uint32_t mapped;
if ((pmp->pm_flags & MSDOSFS_LARGEFS) == 0) {
KASSERT((uint32_t)fileno == fileno,
("fileno >32 bits but not a large fs?"));
return ((uint32_t)fileno);
}
if (fileno < FILENO_FIRST_DYN)
return ((uint32_t)fileno);
mtx_lock(&fileno_mtx);
key.mf_fileno64 = fileno;
mf = RB_FIND(msdosfs_filenotree, &pmp->pm_filenos, &key);
if (mf != NULL) {
mapped = mf->mf_fileno32;
mtx_unlock(&fileno_mtx);
return (mapped);
}
if (pmp->pm_nfileno < FILENO_FIRST_DYN)
panic("msdosfs_fileno_map: wraparound");
mtx_unlock(&fileno_mtx);
mf = malloc(sizeof(*mf), M_MSDOSFSFILENO, M_WAITOK);
mtx_lock(&fileno_mtx);
tmf = RB_FIND(msdosfs_filenotree, &pmp->pm_filenos, &key);
if (tmf != NULL) {
mapped = tmf->mf_fileno32;
mtx_unlock(&fileno_mtx);
free(mf, M_MSDOSFSFILENO);
return (mapped);
}
mf->mf_fileno64 = fileno;
mapped = mf->mf_fileno32 = pmp->pm_nfileno++;
RB_INSERT(msdosfs_filenotree, &pmp->pm_filenos, mf);
mtx_unlock(&fileno_mtx);
return (mapped);
}
/* Compare by 64-bit file number. */
static int
msdosfs_fileno_compare(fa, fb)
struct msdosfs_fileno *fa, *fb;
{
if (fa->mf_fileno64 > fb->mf_fileno64)
return (1);
else if (fa->mf_fileno64 < fb->mf_fileno64)
return (-1);
return (0);
}
RB_GENERATE(msdosfs_filenotree, msdosfs_fileno, mf_tree,
msdosfs_fileno_compare)
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