// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2019 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*/
#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_btree.h"
#include "xfs_ialloc.h"
#include "xfs_ialloc_btree.h"
#include "xfs_iwalk.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_icache.h"
#include "xfs_health.h"
#include "xfs_trans.h"
/*
* Walking Inodes in the Filesystem
* ================================
*
* This iterator function walks a subset of filesystem inodes in increasing
* order from @startino until there are no more inodes. For each allocated
* inode it finds, it calls a walk function with the relevant inode number and
* a pointer to caller-provided data. The walk function can return the usual
* negative error code to stop the iteration; 0 to continue the iteration; or
* XFS_IWALK_ABORT to stop the iteration. This return value is returned to the
* caller.
*
* Internally, we allow the walk function to do anything, which means that we
* cannot maintain the inobt cursor or our lock on the AGI buffer. We
* therefore cache the inobt records in kernel memory and only call the walk
* function when our memory buffer is full. @nr_recs is the number of records
* that we've cached, and @sz_recs is the size of our cache.
*
* It is the responsibility of the walk function to ensure it accesses
* allocated inodes, as the inobt records may be stale by the time they are
* acted upon.
*/
struct xfs_iwalk_ag {
struct xfs_mount *mp;
struct xfs_trans *tp;
/* Where do we start the traversal? */
xfs_ino_t startino;
/* Array of inobt records we cache. */
struct xfs_inobt_rec_incore *recs;
/* Number of entries allocated for the @recs array. */
unsigned int sz_recs;
/* Number of entries in the @recs array that are in use. */
unsigned int nr_recs;
/* Inode walk function and data pointer. */
xfs_iwalk_fn iwalk_fn;
void *data;
};
/*
* Loop over all clusters in a chunk for a given incore inode allocation btree
* record. Do a readahead if there are any allocated inodes in that cluster.
*/
STATIC void
xfs_iwalk_ichunk_ra(
struct xfs_mount *mp,
xfs_agnumber_t agno,
struct xfs_inobt_rec_incore *irec)
{
struct xfs_ino_geometry *igeo = M_IGEO(mp);
xfs_agblock_t agbno;
struct blk_plug plug;
int i; /* inode chunk index */
agbno = XFS_AGINO_TO_AGBNO(mp, irec->ir_startino);
blk_start_plug(&plug);
for (i = 0;
i < XFS_INODES_PER_CHUNK;
i += igeo->inodes_per_cluster,
agbno += igeo->blocks_per_cluster) {
if (xfs_inobt_maskn(i, igeo->inodes_per_cluster) &
~irec->ir_free) {
xfs_btree_reada_bufs(mp, agno, agbno,
igeo->blocks_per_cluster,
&xfs_inode_buf_ops);
}
}
blk_finish_plug(&plug);
}
/*
* Lookup the inode chunk that the given inode lives in and then get the record
* if we found the chunk. If the inode was not the last in the chunk and there
* are some left allocated, update the data for the pointed-to record as well as
* return the count of grabbed inodes.
*/
STATIC int
xfs_iwalk_grab_ichunk(
struct xfs_btree_cur *cur, /* btree cursor */
xfs_agino_t agino, /* starting inode of chunk */
int *icount,/* return # of inodes grabbed */
struct xfs_inobt_rec_incore *irec) /* btree record */
{
int idx; /* index into inode chunk */
int stat;
int error = 0;
/* Lookup the inode chunk that this inode lives in */
error = xfs_inobt_lookup(cur, agino, XFS_LOOKUP_LE, &stat);
if (error)
return error;
if (!stat) {
*icount = 0;
return error;
}
/* Get the record, should always work */
error = xfs_inobt_get_rec(cur, irec, &stat);
if (error)
return error;
XFS_WANT_CORRUPTED_RETURN(cur->bc_mp, stat == 1);
/* Check if the record contains the inode in request */
if (irec->ir_startino + XFS_INODES_PER_CHUNK <= agino) {
*icount = 0;
return 0;
}
idx = agino - irec->ir_startino + 1;
if (idx < XFS_INODES_PER_CHUNK &&
(xfs_inobt_maskn(idx, XFS_INODES_PER_CHUNK - idx) & ~irec->ir_free)) {
int i;
/* We got a right chunk with some left inodes allocated at it.
* Grab the chunk record. Mark all the uninteresting inodes
* free -- because they're before our start point.
*/
for (i = 0; i < idx; i++) {
if (XFS_INOBT_MASK(i) & ~irec->ir_free)
irec->ir_freecount++;
}
irec->ir_free |= xfs_inobt_maskn(0, idx);
*icount = irec->ir_count - irec->ir_freecount;
}
return 0;
}
/* Allocate memory for a walk. */
STATIC int
xfs_iwalk_alloc(
struct xfs_iwalk_ag *iwag)
{
size_t size;
ASSERT(iwag->recs == NULL);
iwag->nr_recs = 0;
/* Allocate a prefetch buffer for inobt records. */
size = iwag->sz_recs * sizeof(struct xfs_inobt_rec_incore);
iwag->recs = kmem_alloc(size, KM_MAYFAIL);
if (iwag->recs == NULL)
return -ENOMEM;
return 0;
}
/* Free memory we allocated for a walk. */
STATIC void
xfs_iwalk_free(
struct xfs_iwalk_ag *iwag)
{
kmem_free(iwag->recs);
iwag->recs = NULL;
}
/* For each inuse inode in each cached inobt record, call our function. */
STATIC int
xfs_iwalk_ag_recs(
struct xfs_iwalk_ag *iwag)
{
struct xfs_mount *mp = iwag->mp;
struct xfs_trans *tp = iwag->tp;
xfs_ino_t ino;
unsigned int i, j;
xfs_agnumber_t agno;
int error;
agno = XFS_INO_TO_AGNO(mp, iwag->startino);
for (i = 0; i < iwag->nr_recs; i++) {
struct xfs_inobt_rec_incore *irec = &iwag->recs[i];
trace_xfs_iwalk_ag_rec(mp, agno, irec);
for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
/* Skip if this inode is free */
if (XFS_INOBT_MASK(j) & irec->ir_free)
continue;
/* Otherwise call our function. */
ino = XFS_AGINO_TO_INO(mp, agno, irec->ir_startino + j);
error = iwag->iwalk_fn(mp, tp, ino, iwag->data);
if (error)
return error;
}
}
return 0;
}
/* Delete cursor and let go of AGI. */
static inline void
xfs_iwalk_del_inobt(
struct xfs_trans *tp,
struct xfs_btree_cur **curpp,
struct xfs_buf **agi_bpp,
int error)
{
if (*curpp) {
xfs_btree_del_cursor(*curpp, error);
*curpp = NULL;
}
if (*agi_bpp) {
xfs_trans_brelse(tp, *agi_bpp);
*agi_bpp = NULL;
}
}
/*
* Set ourselves up for walking inobt records starting from a given point in
* the filesystem.
*
* If caller passed in a nonzero start inode number, load the record from the
* inobt and make the record look like all the inodes before agino are free so
* that we skip them, and then move the cursor to the next inobt record. This
* is how we support starting an iwalk in the middle of an inode chunk.
*
* If the caller passed in a start number of zero, move the cursor to the first
* inobt record.
*
* The caller is responsible for cleaning up the cursor and buffer pointer
* regardless of the error status.
*/
STATIC int
xfs_iwalk_ag_start(
struct xfs_iwalk_ag *iwag,
xfs_agnumber_t agno,
xfs_agino_t agino,
struct xfs_btree_cur **curpp,
struct xfs_buf **agi_bpp,
int *has_more)
{
struct xfs_mount *mp = iwag->mp;
struct xfs_trans *tp = iwag->tp;
int icount;
int error;
/* Set up a fresh cursor and empty the inobt cache. */
iwag->nr_recs = 0;
error = xfs_inobt_cur(mp, tp, agno, XFS_BTNUM_INO, curpp, agi_bpp);
if (error)
return error;
/* Starting at the beginning of the AG? That's easy! */
if (agino == 0)
return xfs_inobt_lookup(*curpp, 0, XFS_LOOKUP_GE, has_more);
/*
* Otherwise, we have to grab the inobt record where we left off, stuff
* the record into our cache, and then see if there are more records.
* We require a lookup cache of at least two elements so that we don't
* have to deal with tearing down the cursor to walk the records.
*/
error = xfs_iwalk_grab_ichunk(*curpp, agino - 1, &icount,
&iwag->recs[iwag->nr_recs]);
if (error)
return error;
if (icount)
iwag->nr_recs++;
/*
* The prefetch calculation is supposed to give us a large enough inobt
* record cache that grab_ichunk can stage a partial first record and
* the loop body can cache a record without having to check for cache
* space until after it reads an inobt record.
*/
ASSERT(iwag->nr_recs < iwag->sz_recs);
return xfs_btree_increment(*curpp, 0, has_more);
}
/*
* The inobt record cache is full, so preserve the inobt cursor state and
* run callbacks on the cached inobt records. When we're done, restore the
* cursor state to wherever the cursor would have been had the cache not been
* full (and therefore we could've just incremented the cursor) if *@has_more
* is true. On exit, *@has_more will indicate whether or not the caller should
* try for more inode records.
*/
STATIC int
xfs_iwalk_run_callbacks(
struct xfs_iwalk_ag *iwag,
xfs_agnumber_t agno,
struct xfs_btree_cur **curpp,
struct xfs_buf **agi_bpp,
int *has_more)
{
struct xfs_mount *mp = iwag->mp;
struct xfs_trans *tp = iwag->tp;
struct xfs_inobt_rec_incore *irec;
xfs_agino_t restart;
int error;
ASSERT(iwag->nr_recs > 0);
/* Delete cursor but remember the last record we cached... */
xfs_iwalk_del_inobt(tp, curpp, agi_bpp, 0);
irec = &iwag->recs[iwag->nr_recs - 1];
restart = irec->ir_startino + XFS_INODES_PER_CHUNK - 1;
error = xfs_iwalk_ag_recs(iwag);
if (error)
return error;
/* ...empty the cache... */
iwag->nr_recs = 0;
if (!has_more)
return 0;
/* ...and recreate the cursor just past where we left off. */
error = xfs_inobt_cur(mp, tp, agno, XFS_BTNUM_INO, curpp, agi_bpp);
if (error)
return error;
return xfs_inobt_lookup(*curpp, restart, XFS_LOOKUP_GE, has_more);
}
/* Walk all inodes in a single AG, from @iwag->startino to the end of the AG. */
STATIC int
xfs_iwalk_ag(
struct xfs_iwalk_ag *iwag)
{
struct xfs_mount *mp = iwag->mp;
struct xfs_trans *tp = iwag->tp;
struct xfs_buf *agi_bp = NULL;
struct xfs_btree_cur *cur = NULL;
xfs_agnumber_t agno;
xfs_agino_t agino;
int has_more;
int error = 0;
/* Set up our cursor at the right place in the inode btree. */
agno = XFS_INO_TO_AGNO(mp, iwag->startino);
agino = XFS_INO_TO_AGINO(mp, iwag->startino);
error = xfs_iwalk_ag_start(iwag, agno, agino, &cur, &agi_bp, &has_more);
while (!error && has_more) {
struct xfs_inobt_rec_incore *irec;
cond_resched();
/* Fetch the inobt record. */
irec = &iwag->recs[iwag->nr_recs];
error = xfs_inobt_get_rec(cur, irec, &has_more);
if (error || !has_more)
break;
/* No allocated inodes in this chunk; skip it. */
if (irec->ir_freecount == irec->ir_count) {
error = xfs_btree_increment(cur, 0, &has_more);
if (error)
break;
continue;
}
/*
* Start readahead for this inode chunk in anticipation of
* walking the inodes.
*/
xfs_iwalk_ichunk_ra(mp, agno, irec);
/*
* If there's space in the buffer for more records, increment
* the btree cursor and grab more.
*/
if (++iwag->nr_recs < iwag->sz_recs) {
error = xfs_btree_increment(cur, 0, &has_more);
if (error || !has_more)
break;
continue;
}
/*
* Otherwise, we need to save cursor state and run the callback
* function on the cached records. The run_callbacks function
* is supposed to return a cursor pointing to the record where
* we would be if we had been able to increment like above.
*/
ASSERT(has_more);
error = xfs_iwalk_run_callbacks(iwag, agno, &cur, &agi_bp,
&has_more);
}
if (iwag->nr_recs == 0 || error)
goto out;
/* Walk the unprocessed records in the cache. */
error = xfs_iwalk_run_callbacks(iwag, agno, &cur, &agi_bp, &has_more);
out:
xfs_iwalk_del_inobt(tp, &cur, &agi_bp, error);
return error;
}
/*
* We experimentally determined that the reduction in ioctl call overhead
* diminishes when userspace asks for more than 2048 inodes, so we'll cap
* prefetch at this point.
*/
#define IWALK_MAX_INODE_PREFETCH (2048U)
/*
* Given the number of inodes to prefetch, set the number of inobt records that
* we cache in memory, which controls the number of inodes we try to read
* ahead. Set the maximum if @inodes == 0.
*/
static inline unsigned int
xfs_iwalk_prefetch(
unsigned int inodes)
{
unsigned int inobt_records;
/*
* If the caller didn't tell us the number of inodes they wanted,
* assume the maximum prefetch possible for best performance.
* Otherwise, cap prefetch at that maximum so that we don't start an
* absurd amount of prefetch.
*/
if (inodes == 0)
inodes = IWALK_MAX_INODE_PREFETCH;
inodes = min(inodes, IWALK_MAX_INODE_PREFETCH);
/* Round the inode count up to a full chunk. */
inodes = round_up(inodes, XFS_INODES_PER_CHUNK);
/*
* In order to convert the number of inodes to prefetch into an
* estimate of the number of inobt records to cache, we require a
* conversion factor that reflects our expectations of the average
* loading factor of an inode chunk. Based on data gathered, most
* (but not all) filesystems manage to keep the inode chunks totally
* full, so we'll underestimate slightly so that our readahead will
* still deliver the performance we want on aging filesystems:
*
* inobt = inodes / (INODES_PER_CHUNK * (4 / 5));
*
* The funny math is to avoid integer division.
*/
inobt_records = (inodes * 5) / (4 * XFS_INODES_PER_CHUNK);
/*
* Allocate enough space to prefetch at least two inobt records so that
* we can cache both the record where the iwalk started and the next
* record. This simplifies the AG inode walk loop setup code.
*/
return max(inobt_records, 2U);
}
/*
* Walk all inodes in the filesystem starting from @startino. The @iwalk_fn
* will be called for each allocated inode, being passed the inode's number and
* @data. @max_prefetch controls how many inobt records' worth of inodes we
* try to readahead.
*/
int
xfs_iwalk(
struct xfs_mount *mp,
struct xfs_trans *tp,
xfs_ino_t startino,
xfs_iwalk_fn iwalk_fn,
unsigned int inode_records,
void *data)
{
struct xfs_iwalk_ag iwag = {
.mp = mp,
.tp = tp,
.iwalk_fn = iwalk_fn,
.data = data,
.startino = startino,
.sz_recs = xfs_iwalk_prefetch(inode_records),
};
xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
int error;
ASSERT(agno < mp->m_sb.sb_agcount);
error = xfs_iwalk_alloc(&iwag);
if (error)
return error;
for (; agno < mp->m_sb.sb_agcount; agno++) {
error = xfs_iwalk_ag(&iwag);
if (error)
break;
iwag.startino = XFS_AGINO_TO_INO(mp, agno + 1, 0);
}
xfs_iwalk_free(&iwag);
return error;
}
