OpenCloudOS-Kernel/fs/xfs/libxfs/xfs_inode_fork.c

768 lines
19 KiB
C

// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2000-2006 Silicon Graphics, Inc.
* All Rights Reserved.
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_inode_item.h"
#include "xfs_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_bmap.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_dir2_priv.h"
#include "xfs_attr_leaf.h"
#include "xfs_types.h"
#include "xfs_errortag.h"
kmem_zone_t *xfs_ifork_zone;
void
xfs_init_local_fork(
struct xfs_inode *ip,
int whichfork,
const void *data,
int64_t size)
{
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
int mem_size = size, real_size = 0;
bool zero_terminate;
/*
* If we are using the local fork to store a symlink body we need to
* zero-terminate it so that we can pass it back to the VFS directly.
* Overallocate the in-memory fork by one for that and add a zero
* to terminate it below.
*/
zero_terminate = S_ISLNK(VFS_I(ip)->i_mode);
if (zero_terminate)
mem_size++;
if (size) {
real_size = roundup(mem_size, 4);
ifp->if_u1.if_data = kmem_alloc(real_size, KM_NOFS);
memcpy(ifp->if_u1.if_data, data, size);
if (zero_terminate)
ifp->if_u1.if_data[size] = '\0';
} else {
ifp->if_u1.if_data = NULL;
}
ifp->if_bytes = size;
ifp->if_flags &= ~(XFS_IFEXTENTS | XFS_IFBROOT);
ifp->if_flags |= XFS_IFINLINE;
}
/*
* The file is in-lined in the on-disk inode.
*/
STATIC int
xfs_iformat_local(
xfs_inode_t *ip,
xfs_dinode_t *dip,
int whichfork,
int size)
{
/*
* If the size is unreasonable, then something
* is wrong and we just bail out rather than crash in
* kmem_alloc() or memcpy() below.
*/
if (unlikely(size > XFS_DFORK_SIZE(dip, ip->i_mount, whichfork))) {
xfs_warn(ip->i_mount,
"corrupt inode %Lu (bad size %d for local fork, size = %zd).",
(unsigned long long) ip->i_ino, size,
XFS_DFORK_SIZE(dip, ip->i_mount, whichfork));
xfs_inode_verifier_error(ip, -EFSCORRUPTED,
"xfs_iformat_local", dip, sizeof(*dip),
__this_address);
return -EFSCORRUPTED;
}
xfs_init_local_fork(ip, whichfork, XFS_DFORK_PTR(dip, whichfork), size);
return 0;
}
/*
* The file consists of a set of extents all of which fit into the on-disk
* inode.
*/
STATIC int
xfs_iformat_extents(
struct xfs_inode *ip,
struct xfs_dinode *dip,
int whichfork)
{
struct xfs_mount *mp = ip->i_mount;
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
int state = xfs_bmap_fork_to_state(whichfork);
int nex = XFS_DFORK_NEXTENTS(dip, whichfork);
int size = nex * sizeof(xfs_bmbt_rec_t);
struct xfs_iext_cursor icur;
struct xfs_bmbt_rec *dp;
struct xfs_bmbt_irec new;
int i;
/*
* If the number of extents is unreasonable, then something is wrong and
* we just bail out rather than crash in kmem_alloc() or memcpy() below.
*/
if (unlikely(size < 0 || size > XFS_DFORK_SIZE(dip, mp, whichfork))) {
xfs_warn(ip->i_mount, "corrupt inode %Lu ((a)extents = %d).",
(unsigned long long) ip->i_ino, nex);
xfs_inode_verifier_error(ip, -EFSCORRUPTED,
"xfs_iformat_extents(1)", dip, sizeof(*dip),
__this_address);
return -EFSCORRUPTED;
}
ifp->if_bytes = 0;
ifp->if_u1.if_root = NULL;
ifp->if_height = 0;
if (size) {
dp = (xfs_bmbt_rec_t *) XFS_DFORK_PTR(dip, whichfork);
xfs_iext_first(ifp, &icur);
for (i = 0; i < nex; i++, dp++) {
xfs_failaddr_t fa;
xfs_bmbt_disk_get_all(dp, &new);
fa = xfs_bmap_validate_extent(ip, whichfork, &new);
if (fa) {
xfs_inode_verifier_error(ip, -EFSCORRUPTED,
"xfs_iformat_extents(2)",
dp, sizeof(*dp), fa);
return -EFSCORRUPTED;
}
xfs_iext_insert(ip, &icur, &new, state);
trace_xfs_read_extent(ip, &icur, state, _THIS_IP_);
xfs_iext_next(ifp, &icur);
}
}
ifp->if_flags |= XFS_IFEXTENTS;
return 0;
}
/*
* The file has too many extents to fit into
* the inode, so they are in B-tree format.
* Allocate a buffer for the root of the B-tree
* and copy the root into it. The i_extents
* field will remain NULL until all of the
* extents are read in (when they are needed).
*/
STATIC int
xfs_iformat_btree(
xfs_inode_t *ip,
xfs_dinode_t *dip,
int whichfork)
{
struct xfs_mount *mp = ip->i_mount;
xfs_bmdr_block_t *dfp;
struct xfs_ifork *ifp;
/* REFERENCED */
int nrecs;
int size;
int level;
ifp = XFS_IFORK_PTR(ip, whichfork);
dfp = (xfs_bmdr_block_t *)XFS_DFORK_PTR(dip, whichfork);
size = XFS_BMAP_BROOT_SPACE(mp, dfp);
nrecs = be16_to_cpu(dfp->bb_numrecs);
level = be16_to_cpu(dfp->bb_level);
/*
* blow out if -- fork has less extents than can fit in
* fork (fork shouldn't be a btree format), root btree
* block has more records than can fit into the fork,
* or the number of extents is greater than the number of
* blocks.
*/
if (unlikely(ifp->if_nextents <= XFS_IFORK_MAXEXT(ip, whichfork) ||
nrecs == 0 ||
XFS_BMDR_SPACE_CALC(nrecs) >
XFS_DFORK_SIZE(dip, mp, whichfork) ||
ifp->if_nextents > ip->i_d.di_nblocks) ||
level == 0 || level > XFS_BM_MAXLEVELS(mp, whichfork)) {
xfs_warn(mp, "corrupt inode %Lu (btree).",
(unsigned long long) ip->i_ino);
xfs_inode_verifier_error(ip, -EFSCORRUPTED,
"xfs_iformat_btree", dfp, size,
__this_address);
return -EFSCORRUPTED;
}
ifp->if_broot_bytes = size;
ifp->if_broot = kmem_alloc(size, KM_NOFS);
ASSERT(ifp->if_broot != NULL);
/*
* Copy and convert from the on-disk structure
* to the in-memory structure.
*/
xfs_bmdr_to_bmbt(ip, dfp, XFS_DFORK_SIZE(dip, ip->i_mount, whichfork),
ifp->if_broot, size);
ifp->if_flags &= ~XFS_IFEXTENTS;
ifp->if_flags |= XFS_IFBROOT;
ifp->if_bytes = 0;
ifp->if_u1.if_root = NULL;
ifp->if_height = 0;
return 0;
}
int
xfs_iformat_data_fork(
struct xfs_inode *ip,
struct xfs_dinode *dip)
{
struct inode *inode = VFS_I(ip);
int error;
/*
* Initialize the extent count early, as the per-format routines may
* depend on it.
*/
ip->i_df.if_format = dip->di_format;
ip->i_df.if_nextents = be32_to_cpu(dip->di_nextents);
switch (inode->i_mode & S_IFMT) {
case S_IFIFO:
case S_IFCHR:
case S_IFBLK:
case S_IFSOCK:
ip->i_disk_size = 0;
inode->i_rdev = xfs_to_linux_dev_t(xfs_dinode_get_rdev(dip));
return 0;
case S_IFREG:
case S_IFLNK:
case S_IFDIR:
switch (ip->i_df.if_format) {
case XFS_DINODE_FMT_LOCAL:
error = xfs_iformat_local(ip, dip, XFS_DATA_FORK,
be64_to_cpu(dip->di_size));
if (!error)
error = xfs_ifork_verify_local_data(ip);
return error;
case XFS_DINODE_FMT_EXTENTS:
return xfs_iformat_extents(ip, dip, XFS_DATA_FORK);
case XFS_DINODE_FMT_BTREE:
return xfs_iformat_btree(ip, dip, XFS_DATA_FORK);
default:
xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__,
dip, sizeof(*dip), __this_address);
return -EFSCORRUPTED;
}
break;
default:
xfs_inode_verifier_error(ip, -EFSCORRUPTED, __func__, dip,
sizeof(*dip), __this_address);
return -EFSCORRUPTED;
}
}
static uint16_t
xfs_dfork_attr_shortform_size(
struct xfs_dinode *dip)
{
struct xfs_attr_shortform *atp =
(struct xfs_attr_shortform *)XFS_DFORK_APTR(dip);
return be16_to_cpu(atp->hdr.totsize);
}
struct xfs_ifork *
xfs_ifork_alloc(
enum xfs_dinode_fmt format,
xfs_extnum_t nextents)
{
struct xfs_ifork *ifp;
ifp = kmem_cache_zalloc(xfs_ifork_zone, GFP_NOFS | __GFP_NOFAIL);
ifp->if_format = format;
ifp->if_nextents = nextents;
return ifp;
}
int
xfs_iformat_attr_fork(
struct xfs_inode *ip,
struct xfs_dinode *dip)
{
int error = 0;
/*
* Initialize the extent count early, as the per-format routines may
* depend on it.
*/
ip->i_afp = xfs_ifork_alloc(dip->di_aformat,
be16_to_cpu(dip->di_anextents));
switch (ip->i_afp->if_format) {
case XFS_DINODE_FMT_LOCAL:
error = xfs_iformat_local(ip, dip, XFS_ATTR_FORK,
xfs_dfork_attr_shortform_size(dip));
if (!error)
error = xfs_ifork_verify_local_attr(ip);
break;
case XFS_DINODE_FMT_EXTENTS:
error = xfs_iformat_extents(ip, dip, XFS_ATTR_FORK);
break;
case XFS_DINODE_FMT_BTREE:
error = xfs_iformat_btree(ip, dip, XFS_ATTR_FORK);
break;
default:
xfs_inode_verifier_error(ip, error, __func__, dip,
sizeof(*dip), __this_address);
error = -EFSCORRUPTED;
break;
}
if (error) {
kmem_cache_free(xfs_ifork_zone, ip->i_afp);
ip->i_afp = NULL;
}
return error;
}
/*
* Reallocate the space for if_broot based on the number of records
* being added or deleted as indicated in rec_diff. Move the records
* and pointers in if_broot to fit the new size. When shrinking this
* will eliminate holes between the records and pointers created by
* the caller. When growing this will create holes to be filled in
* by the caller.
*
* The caller must not request to add more records than would fit in
* the on-disk inode root. If the if_broot is currently NULL, then
* if we are adding records, one will be allocated. The caller must also
* not request that the number of records go below zero, although
* it can go to zero.
*
* ip -- the inode whose if_broot area is changing
* ext_diff -- the change in the number of records, positive or negative,
* requested for the if_broot array.
*/
void
xfs_iroot_realloc(
xfs_inode_t *ip,
int rec_diff,
int whichfork)
{
struct xfs_mount *mp = ip->i_mount;
int cur_max;
struct xfs_ifork *ifp;
struct xfs_btree_block *new_broot;
int new_max;
size_t new_size;
char *np;
char *op;
/*
* Handle the degenerate case quietly.
*/
if (rec_diff == 0) {
return;
}
ifp = XFS_IFORK_PTR(ip, whichfork);
if (rec_diff > 0) {
/*
* If there wasn't any memory allocated before, just
* allocate it now and get out.
*/
if (ifp->if_broot_bytes == 0) {
new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, rec_diff);
ifp->if_broot = kmem_alloc(new_size, KM_NOFS);
ifp->if_broot_bytes = (int)new_size;
return;
}
/*
* If there is already an existing if_broot, then we need
* to realloc() it and shift the pointers to their new
* location. The records don't change location because
* they are kept butted up against the btree block header.
*/
cur_max = xfs_bmbt_maxrecs(mp, ifp->if_broot_bytes, 0);
new_max = cur_max + rec_diff;
new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, new_max);
ifp->if_broot = krealloc(ifp->if_broot, new_size,
GFP_NOFS | __GFP_NOFAIL);
op = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
ifp->if_broot_bytes);
np = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
(int)new_size);
ifp->if_broot_bytes = (int)new_size;
ASSERT(XFS_BMAP_BMDR_SPACE(ifp->if_broot) <=
XFS_IFORK_SIZE(ip, whichfork));
memmove(np, op, cur_max * (uint)sizeof(xfs_fsblock_t));
return;
}
/*
* rec_diff is less than 0. In this case, we are shrinking the
* if_broot buffer. It must already exist. If we go to zero
* records, just get rid of the root and clear the status bit.
*/
ASSERT((ifp->if_broot != NULL) && (ifp->if_broot_bytes > 0));
cur_max = xfs_bmbt_maxrecs(mp, ifp->if_broot_bytes, 0);
new_max = cur_max + rec_diff;
ASSERT(new_max >= 0);
if (new_max > 0)
new_size = XFS_BMAP_BROOT_SPACE_CALC(mp, new_max);
else
new_size = 0;
if (new_size > 0) {
new_broot = kmem_alloc(new_size, KM_NOFS);
/*
* First copy over the btree block header.
*/
memcpy(new_broot, ifp->if_broot,
XFS_BMBT_BLOCK_LEN(ip->i_mount));
} else {
new_broot = NULL;
ifp->if_flags &= ~XFS_IFBROOT;
}
/*
* Only copy the records and pointers if there are any.
*/
if (new_max > 0) {
/*
* First copy the records.
*/
op = (char *)XFS_BMBT_REC_ADDR(mp, ifp->if_broot, 1);
np = (char *)XFS_BMBT_REC_ADDR(mp, new_broot, 1);
memcpy(np, op, new_max * (uint)sizeof(xfs_bmbt_rec_t));
/*
* Then copy the pointers.
*/
op = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, ifp->if_broot, 1,
ifp->if_broot_bytes);
np = (char *)XFS_BMAP_BROOT_PTR_ADDR(mp, new_broot, 1,
(int)new_size);
memcpy(np, op, new_max * (uint)sizeof(xfs_fsblock_t));
}
kmem_free(ifp->if_broot);
ifp->if_broot = new_broot;
ifp->if_broot_bytes = (int)new_size;
if (ifp->if_broot)
ASSERT(XFS_BMAP_BMDR_SPACE(ifp->if_broot) <=
XFS_IFORK_SIZE(ip, whichfork));
return;
}
/*
* This is called when the amount of space needed for if_data
* is increased or decreased. The change in size is indicated by
* the number of bytes that need to be added or deleted in the
* byte_diff parameter.
*
* If the amount of space needed has decreased below the size of the
* inline buffer, then switch to using the inline buffer. Otherwise,
* use kmem_realloc() or kmem_alloc() to adjust the size of the buffer
* to what is needed.
*
* ip -- the inode whose if_data area is changing
* byte_diff -- the change in the number of bytes, positive or negative,
* requested for the if_data array.
*/
void
xfs_idata_realloc(
struct xfs_inode *ip,
int64_t byte_diff,
int whichfork)
{
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
int64_t new_size = ifp->if_bytes + byte_diff;
ASSERT(new_size >= 0);
ASSERT(new_size <= XFS_IFORK_SIZE(ip, whichfork));
if (byte_diff == 0)
return;
if (new_size == 0) {
kmem_free(ifp->if_u1.if_data);
ifp->if_u1.if_data = NULL;
ifp->if_bytes = 0;
return;
}
/*
* For inline data, the underlying buffer must be a multiple of 4 bytes
* in size so that it can be logged and stay on word boundaries.
* We enforce that here.
*/
ifp->if_u1.if_data = krealloc(ifp->if_u1.if_data, roundup(new_size, 4),
GFP_NOFS | __GFP_NOFAIL);
ifp->if_bytes = new_size;
}
void
xfs_idestroy_fork(
struct xfs_ifork *ifp)
{
if (ifp->if_broot != NULL) {
kmem_free(ifp->if_broot);
ifp->if_broot = NULL;
}
/*
* If the format is local, then we can't have an extents array so just
* look for an inline data array. If we're not local then we may or may
* not have an extents list, so check and free it up if we do.
*/
if (ifp->if_format == XFS_DINODE_FMT_LOCAL) {
kmem_free(ifp->if_u1.if_data);
ifp->if_u1.if_data = NULL;
} else if (ifp->if_flags & XFS_IFEXTENTS) {
if (ifp->if_height)
xfs_iext_destroy(ifp);
}
}
/*
* Convert in-core extents to on-disk form
*
* In the case of the data fork, the in-core and on-disk fork sizes can be
* different due to delayed allocation extents. We only copy on-disk extents
* here, so callers must always use the physical fork size to determine the
* size of the buffer passed to this routine. We will return the size actually
* used.
*/
int
xfs_iextents_copy(
struct xfs_inode *ip,
struct xfs_bmbt_rec *dp,
int whichfork)
{
int state = xfs_bmap_fork_to_state(whichfork);
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
struct xfs_iext_cursor icur;
struct xfs_bmbt_irec rec;
int64_t copied = 0;
ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL | XFS_ILOCK_SHARED));
ASSERT(ifp->if_bytes > 0);
for_each_xfs_iext(ifp, &icur, &rec) {
if (isnullstartblock(rec.br_startblock))
continue;
ASSERT(xfs_bmap_validate_extent(ip, whichfork, &rec) == NULL);
xfs_bmbt_disk_set_all(dp, &rec);
trace_xfs_write_extent(ip, &icur, state, _RET_IP_);
copied += sizeof(struct xfs_bmbt_rec);
dp++;
}
ASSERT(copied > 0);
ASSERT(copied <= ifp->if_bytes);
return copied;
}
/*
* Each of the following cases stores data into the same region
* of the on-disk inode, so only one of them can be valid at
* any given time. While it is possible to have conflicting formats
* and log flags, e.g. having XFS_ILOG_?DATA set when the fork is
* in EXTENTS format, this can only happen when the fork has
* changed formats after being modified but before being flushed.
* In these cases, the format always takes precedence, because the
* format indicates the current state of the fork.
*/
void
xfs_iflush_fork(
xfs_inode_t *ip,
xfs_dinode_t *dip,
struct xfs_inode_log_item *iip,
int whichfork)
{
char *cp;
struct xfs_ifork *ifp;
xfs_mount_t *mp;
static const short brootflag[2] =
{ XFS_ILOG_DBROOT, XFS_ILOG_ABROOT };
static const short dataflag[2] =
{ XFS_ILOG_DDATA, XFS_ILOG_ADATA };
static const short extflag[2] =
{ XFS_ILOG_DEXT, XFS_ILOG_AEXT };
if (!iip)
return;
ifp = XFS_IFORK_PTR(ip, whichfork);
/*
* This can happen if we gave up in iformat in an error path,
* for the attribute fork.
*/
if (!ifp) {
ASSERT(whichfork == XFS_ATTR_FORK);
return;
}
cp = XFS_DFORK_PTR(dip, whichfork);
mp = ip->i_mount;
switch (ifp->if_format) {
case XFS_DINODE_FMT_LOCAL:
if ((iip->ili_fields & dataflag[whichfork]) &&
(ifp->if_bytes > 0)) {
ASSERT(ifp->if_u1.if_data != NULL);
ASSERT(ifp->if_bytes <= XFS_IFORK_SIZE(ip, whichfork));
memcpy(cp, ifp->if_u1.if_data, ifp->if_bytes);
}
break;
case XFS_DINODE_FMT_EXTENTS:
ASSERT((ifp->if_flags & XFS_IFEXTENTS) ||
!(iip->ili_fields & extflag[whichfork]));
if ((iip->ili_fields & extflag[whichfork]) &&
(ifp->if_bytes > 0)) {
ASSERT(ifp->if_nextents > 0);
(void)xfs_iextents_copy(ip, (xfs_bmbt_rec_t *)cp,
whichfork);
}
break;
case XFS_DINODE_FMT_BTREE:
if ((iip->ili_fields & brootflag[whichfork]) &&
(ifp->if_broot_bytes > 0)) {
ASSERT(ifp->if_broot != NULL);
ASSERT(XFS_BMAP_BMDR_SPACE(ifp->if_broot) <=
XFS_IFORK_SIZE(ip, whichfork));
xfs_bmbt_to_bmdr(mp, ifp->if_broot, ifp->if_broot_bytes,
(xfs_bmdr_block_t *)cp,
XFS_DFORK_SIZE(dip, mp, whichfork));
}
break;
case XFS_DINODE_FMT_DEV:
if (iip->ili_fields & XFS_ILOG_DEV) {
ASSERT(whichfork == XFS_DATA_FORK);
xfs_dinode_put_rdev(dip,
linux_to_xfs_dev_t(VFS_I(ip)->i_rdev));
}
break;
default:
ASSERT(0);
break;
}
}
/* Convert bmap state flags to an inode fork. */
struct xfs_ifork *
xfs_iext_state_to_fork(
struct xfs_inode *ip,
int state)
{
if (state & BMAP_COWFORK)
return ip->i_cowfp;
else if (state & BMAP_ATTRFORK)
return ip->i_afp;
return &ip->i_df;
}
/*
* Initialize an inode's copy-on-write fork.
*/
void
xfs_ifork_init_cow(
struct xfs_inode *ip)
{
if (ip->i_cowfp)
return;
ip->i_cowfp = kmem_cache_zalloc(xfs_ifork_zone,
GFP_NOFS | __GFP_NOFAIL);
ip->i_cowfp->if_flags = XFS_IFEXTENTS;
ip->i_cowfp->if_format = XFS_DINODE_FMT_EXTENTS;
}
/* Verify the inline contents of the data fork of an inode. */
int
xfs_ifork_verify_local_data(
struct xfs_inode *ip)
{
xfs_failaddr_t fa = NULL;
switch (VFS_I(ip)->i_mode & S_IFMT) {
case S_IFDIR:
fa = xfs_dir2_sf_verify(ip);
break;
case S_IFLNK:
fa = xfs_symlink_shortform_verify(ip);
break;
default:
break;
}
if (fa) {
xfs_inode_verifier_error(ip, -EFSCORRUPTED, "data fork",
ip->i_df.if_u1.if_data, ip->i_df.if_bytes, fa);
return -EFSCORRUPTED;
}
return 0;
}
/* Verify the inline contents of the attr fork of an inode. */
int
xfs_ifork_verify_local_attr(
struct xfs_inode *ip)
{
struct xfs_ifork *ifp = ip->i_afp;
xfs_failaddr_t fa;
if (!ifp)
fa = __this_address;
else
fa = xfs_attr_shortform_verify(ip);
if (fa) {
xfs_inode_verifier_error(ip, -EFSCORRUPTED, "attr fork",
ifp ? ifp->if_u1.if_data : NULL,
ifp ? ifp->if_bytes : 0, fa);
return -EFSCORRUPTED;
}
return 0;
}
int
xfs_iext_count_may_overflow(
struct xfs_inode *ip,
int whichfork,
int nr_to_add)
{
struct xfs_ifork *ifp = XFS_IFORK_PTR(ip, whichfork);
uint64_t max_exts;
uint64_t nr_exts;
if (whichfork == XFS_COW_FORK)
return 0;
max_exts = (whichfork == XFS_ATTR_FORK) ? MAXAEXTNUM : MAXEXTNUM;
if (XFS_TEST_ERROR(false, ip->i_mount, XFS_ERRTAG_REDUCE_MAX_IEXTENTS))
max_exts = 10;
nr_exts = ifp->if_nextents + nr_to_add;
if (nr_exts < ifp->if_nextents || nr_exts > max_exts)
return -EFBIG;
return 0;
}