linux/fs/xfs/xfs_iwalk.c

782 lines
21 KiB
C
Raw Normal View History

// 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"
#include "xfs_pwork.h"
#include "xfs_ag.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
* -ECANCELED 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 {
/* parallel work control data; will be null if single threaded */
struct xfs_pwork pwork;
struct xfs_mount *mp;
struct xfs_trans *tp;
struct xfs_perag *pag;
/* Where do we start the traversal? */
xfs_ino_t startino;
/* What was the last inode number we saw when iterating the inobt? */
xfs_ino_t lastino;
/* 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;
xfs_inobt_walk_fn inobt_walk_fn;
void *data;
/*
* Make it look like the inodes up to startino are free so that
* bulkstat can start its inode iteration at the correct place without
* needing to special case everywhere.
*/
unsigned int trim_start:1;
/* Skip empty inobt records? */
unsigned int skip_empty:1;
/* Drop the (hopefully empty) transaction when calling iwalk_fn. */
unsigned int drop_trans:1;
};
/*
* 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,
struct xfs_perag *pag,
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) {
xfs_inofree_t imask;
imask = xfs_inobt_maskn(i, igeo->inodes_per_cluster);
if (imask & ~irec->ir_free) {
xfs_btree_reada_bufs(mp, pag->pag_agno, agbno,
igeo->blocks_per_cluster,
&xfs_inode_buf_ops);
}
agbno += igeo->blocks_per_cluster;
}
blk_finish_plug(&plug);
}
/*
* Set the bits in @irec's free mask that correspond to the inodes before
* @agino so that we skip them. This is how we restart an inode walk that was
* interrupted in the middle of an inode record.
*/
STATIC void
xfs_iwalk_adjust_start(
xfs_agino_t agino, /* starting inode of chunk */
struct xfs_inobt_rec_incore *irec) /* btree record */
{
int idx; /* index into inode chunk */
int i;
idx = agino - irec->ir_startino;
/*
* 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);
}
/* 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;
struct xfs_perag *pag = iwag->pag;
xfs_ino_t ino;
unsigned int i, j;
int error;
for (i = 0; i < iwag->nr_recs; i++) {
struct xfs_inobt_rec_incore *irec = &iwag->recs[i];
trace_xfs_iwalk_ag_rec(mp, pag->pag_agno, irec);
if (xfs_pwork_want_abort(&iwag->pwork))
return 0;
if (iwag->inobt_walk_fn) {
error = iwag->inobt_walk_fn(mp, tp, pag->pag_agno, irec,
iwag->data);
if (error)
return error;
}
if (!iwag->iwalk_fn)
continue;
for (j = 0; j < XFS_INODES_PER_CHUNK; j++) {
if (xfs_pwork_want_abort(&iwag->pwork))
return 0;
/* 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, pag->pag_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_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;
struct xfs_perag *pag = iwag->pag;
struct xfs_inobt_rec_incore *irec;
int error;
/* Set up a fresh cursor and empty the inobt cache. */
iwag->nr_recs = 0;
error = xfs_inobt_cur(pag, tp, 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 the
* caller doesn't have to deal with tearing down the cursor to walk the
* records.
*/
error = xfs_inobt_lookup(*curpp, agino, XFS_LOOKUP_LE, has_more);
if (error)
return error;
/*
* If the LE lookup at @agino yields no records, jump ahead to the
* inobt cursor increment to see if there are more records to process.
*/
if (!*has_more)
goto out_advance;
/* Get the record, should always work */
irec = &iwag->recs[iwag->nr_recs];
error = xfs_inobt_get_rec(*curpp, irec, has_more);
if (error)
return error;
xfs: kill the XFS_WANT_CORRUPT_* macros The XFS_WANT_CORRUPT_* macros conceal subtle side effects such as the creation of local variables and redirections of the code flow. This is pretty ugly, so replace them with explicit XFS_IS_CORRUPT tests that remove both of those ugly points. The change was performed with the following coccinelle script: @@ expression mp, test; identifier label; @@ - XFS_WANT_CORRUPTED_GOTO(mp, test, label); + if (XFS_IS_CORRUPT(mp, !test)) { error = -EFSCORRUPTED; goto label; } @@ expression mp, test; @@ - XFS_WANT_CORRUPTED_RETURN(mp, test); + if (XFS_IS_CORRUPT(mp, !test)) return -EFSCORRUPTED; @@ expression mp, lval, rval; @@ - XFS_IS_CORRUPT(mp, !(lval == rval)) + XFS_IS_CORRUPT(mp, lval != rval) @@ expression mp, e1, e2; @@ - XFS_IS_CORRUPT(mp, !(e1 && e2)) + XFS_IS_CORRUPT(mp, !e1 || !e2) @@ expression e1, e2; @@ - !(e1 == e2) + e1 != e2 @@ expression e1, e2, e3, e4, e5, e6; @@ - !(e1 == e2 && e3 == e4) || e5 != e6 + e1 != e2 || e3 != e4 || e5 != e6 @@ expression e1, e2, e3, e4, e5, e6; @@ - !(e1 == e2 || (e3 <= e4 && e5 <= e6)) + e1 != e2 && (e3 > e4 || e5 > e6) @@ expression mp, e1, e2; @@ - XFS_IS_CORRUPT(mp, !(e1 <= e2)) + XFS_IS_CORRUPT(mp, e1 > e2) @@ expression mp, e1, e2; @@ - XFS_IS_CORRUPT(mp, !(e1 < e2)) + XFS_IS_CORRUPT(mp, e1 >= e2) @@ expression mp, e1; @@ - XFS_IS_CORRUPT(mp, !!e1) + XFS_IS_CORRUPT(mp, e1) @@ expression mp, e1, e2; @@ - XFS_IS_CORRUPT(mp, !(e1 || e2)) + XFS_IS_CORRUPT(mp, !e1 && !e2) @@ expression mp, e1, e2, e3, e4; @@ - XFS_IS_CORRUPT(mp, !(e1 == e2) && !(e3 == e4)) + XFS_IS_CORRUPT(mp, e1 != e2 && e3 != e4) @@ expression mp, e1, e2, e3, e4; @@ - XFS_IS_CORRUPT(mp, !(e1 <= e2) || !(e3 >= e4)) + XFS_IS_CORRUPT(mp, e1 > e2 || e3 < e4) @@ expression mp, e1, e2, e3, e4; @@ - XFS_IS_CORRUPT(mp, !(e1 == e2) && !(e3 <= e4)) + XFS_IS_CORRUPT(mp, e1 != e2 && e3 > e4) Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
2019-11-11 20:52:18 +00:00
if (XFS_IS_CORRUPT(mp, *has_more != 1))
return -EFSCORRUPTED;
iwag->lastino = XFS_AGINO_TO_INO(mp, pag->pag_agno,
irec->ir_startino + XFS_INODES_PER_CHUNK - 1);
/*
* If the LE lookup yielded an inobt record before the cursor position,
* skip it and see if there's another one after it.
*/
if (irec->ir_startino + XFS_INODES_PER_CHUNK <= agino)
goto out_advance;
/*
* If agino fell in the middle of the inode record, make it look like
* the inodes up to agino are free so that we don't return them again.
*/
if (iwag->trim_start)
xfs_iwalk_adjust_start(agino, irec);
/*
* 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.
*/
iwag->nr_recs++;
ASSERT(iwag->nr_recs < iwag->sz_recs);
out_advance:
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,
struct xfs_btree_cur **curpp,
struct xfs_buf **agi_bpp,
int *has_more)
{
struct xfs_mount *mp = iwag->mp;
struct xfs_inobt_rec_incore *irec;
xfs_agino_t next_agino;
int error;
next_agino = XFS_INO_TO_AGINO(mp, iwag->lastino) + 1;
ASSERT(iwag->nr_recs > 0);
/* Delete cursor but remember the last record we cached... */
xfs_iwalk_del_inobt(iwag->tp, curpp, agi_bpp, 0);
irec = &iwag->recs[iwag->nr_recs - 1];
ASSERT(next_agino >= irec->ir_startino + XFS_INODES_PER_CHUNK);
if (iwag->drop_trans) {
xfs_trans_cancel(iwag->tp);
iwag->tp = NULL;
}
error = xfs_iwalk_ag_recs(iwag);
if (error)
return error;
/* ...empty the cache... */
iwag->nr_recs = 0;
if (!has_more)
return 0;
if (iwag->drop_trans) {
error = xfs_trans_alloc_empty(mp, &iwag->tp);
if (error)
return error;
}
/* ...and recreate the cursor just past where we left off. */
error = xfs_inobt_cur(iwag->pag, iwag->tp, XFS_BTNUM_INO, curpp,
agi_bpp);
if (error)
return error;
return xfs_inobt_lookup(*curpp, next_agino, 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_perag *pag = iwag->pag;
struct xfs_buf *agi_bp = NULL;
struct xfs_btree_cur *cur = NULL;
xfs_agino_t agino;
int has_more;
int error = 0;
/* Set up our cursor at the right place in the inode btree. */
ASSERT(pag->pag_agno == XFS_INO_TO_AGNO(mp, iwag->startino));
agino = XFS_INO_TO_AGINO(mp, iwag->startino);
error = xfs_iwalk_ag_start(iwag, agino, &cur, &agi_bp, &has_more);
while (!error && has_more) {
struct xfs_inobt_rec_incore *irec;
xfs_ino_t rec_fsino;
cond_resched();
if (xfs_pwork_want_abort(&iwag->pwork))
goto out;
/* Fetch the inobt record. */
irec = &iwag->recs[iwag->nr_recs];
error = xfs_inobt_get_rec(cur, irec, &has_more);
if (error || !has_more)
break;
/* Make sure that we always move forward. */
rec_fsino = XFS_AGINO_TO_INO(mp, pag->pag_agno, irec->ir_startino);
if (iwag->lastino != NULLFSINO &&
XFS_IS_CORRUPT(mp, iwag->lastino >= rec_fsino)) {
error = -EFSCORRUPTED;
goto out;
}
iwag->lastino = rec_fsino + XFS_INODES_PER_CHUNK - 1;
/* No allocated inodes in this chunk; skip it. */
if (iwag->skip_empty && 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.
*/
if (iwag->iwalk_fn)
xfs_iwalk_ichunk_ra(mp, pag, 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, &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, &cur, &agi_bp, &has_more);
out:
xfs_iwalk_del_inobt(iwag->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,
unsigned int flags,
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),
.trim_start = 1,
.skip_empty = 1,
.pwork = XFS_PWORK_SINGLE_THREADED,
.lastino = NULLFSINO,
};
struct xfs_perag *pag;
xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
int error;
ASSERT(agno < mp->m_sb.sb_agcount);
ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));
error = xfs_iwalk_alloc(&iwag);
if (error)
return error;
for_each_perag_from(mp, agno, pag) {
iwag.pag = pag;
error = xfs_iwalk_ag(&iwag);
if (error)
break;
iwag.startino = XFS_AGINO_TO_INO(mp, agno + 1, 0);
if (flags & XFS_INOBT_WALK_SAME_AG)
break;
iwag.pag = NULL;
}
if (iwag.pag)
xfs: active perag reference counting We need to be able to dynamically remove instantiated AGs from memory safely, either for shrinking the filesystem or paging AG state in and out of memory (e.g. supporting millions of AGs). This means we need to be able to safely exclude operations from accessing perags while dynamic removal is in progress. To do this, introduce the concept of active and passive references. Active references are required for high level operations that make use of an AG for a given operation (e.g. allocation) and pin the perag in memory for the duration of the operation that is operating on the perag (e.g. transaction scope). This means we can fail to get an active reference to an AG, hence callers of the new active reference API must be able to handle lookup failure gracefully. Passive references are used in low level code, where we might need to access the perag structure for the purposes of completing high level operations. For example, buffers need to use passive references because: - we need to be able to do metadata IO during operations like grow and shrink transactions where high level active references to the AG have already been blocked - buffers need to pin the perag until they are reclaimed from memory, something that high level code has no direct control over. - unused cached buffers should not prevent a shrink from being started. Hence we have active references that will form exclusion barriers for operations to be performed on an AG, and passive references that will prevent reclaim of the perag until all objects with passive references have been reclaimed themselves. This patch introduce xfs_perag_grab()/xfs_perag_rele() as the API for active AG reference functionality. We also need to convert the for_each_perag*() iterators to use active references, which will start the process of converting high level code over to using active references. Conversion of non-iterator based code to active references will be done in followup patches. Note that the implementation using reference counting is really just a development vehicle for the API to ensure we don't have any leaks in the callers. Once we need to remove perag structures from memory dyanmically, we will need a much more robust per-ag state transition mechanism for preventing new references from being taken while we wait for existing references to drain before removal from memory can occur.... Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Allison Henderson <allison.henderson@oracle.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2023-02-12 22:14:42 +00:00
xfs_perag_rele(pag);
xfs_iwalk_free(&iwag);
return error;
}
/* Run per-thread iwalk work. */
static int
xfs_iwalk_ag_work(
struct xfs_mount *mp,
struct xfs_pwork *pwork)
{
struct xfs_iwalk_ag *iwag;
int error = 0;
iwag = container_of(pwork, struct xfs_iwalk_ag, pwork);
if (xfs_pwork_want_abort(pwork))
goto out;
error = xfs_iwalk_alloc(iwag);
if (error)
goto out;
/*
* Grab an empty transaction so that we can use its recursive buffer
* locking abilities to detect cycles in the inobt without deadlocking.
*/
error = xfs_trans_alloc_empty(mp, &iwag->tp);
if (error)
goto out;
iwag->drop_trans = 1;
error = xfs_iwalk_ag(iwag);
if (iwag->tp)
xfs_trans_cancel(iwag->tp);
xfs_iwalk_free(iwag);
out:
xfs_perag_put(iwag->pag);
kmem_free(iwag);
return error;
}
/*
* Walk all the inodes in the filesystem using multiple threads to process each
* AG.
*/
int
xfs_iwalk_threaded(
struct xfs_mount *mp,
xfs_ino_t startino,
unsigned int flags,
xfs_iwalk_fn iwalk_fn,
unsigned int inode_records,
bool polled,
void *data)
{
struct xfs_pwork_ctl pctl;
struct xfs_perag *pag;
xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
int error;
ASSERT(agno < mp->m_sb.sb_agcount);
ASSERT(!(flags & ~XFS_IWALK_FLAGS_ALL));
error = xfs_pwork_init(mp, &pctl, xfs_iwalk_ag_work, "xfs_iwalk");
if (error)
return error;
for_each_perag_from(mp, agno, pag) {
struct xfs_iwalk_ag *iwag;
if (xfs_pwork_ctl_want_abort(&pctl))
break;
iwag = kmem_zalloc(sizeof(struct xfs_iwalk_ag), 0);
iwag->mp = mp;
/*
* perag is being handed off to async work, so take a passive
* reference for the async work to release.
*/
iwag->pag = xfs_perag_hold(pag);
iwag->iwalk_fn = iwalk_fn;
iwag->data = data;
iwag->startino = startino;
iwag->sz_recs = xfs_iwalk_prefetch(inode_records);
iwag->lastino = NULLFSINO;
xfs_pwork_queue(&pctl, &iwag->pwork);
startino = XFS_AGINO_TO_INO(mp, pag->pag_agno + 1, 0);
if (flags & XFS_INOBT_WALK_SAME_AG)
break;
}
if (pag)
xfs: active perag reference counting We need to be able to dynamically remove instantiated AGs from memory safely, either for shrinking the filesystem or paging AG state in and out of memory (e.g. supporting millions of AGs). This means we need to be able to safely exclude operations from accessing perags while dynamic removal is in progress. To do this, introduce the concept of active and passive references. Active references are required for high level operations that make use of an AG for a given operation (e.g. allocation) and pin the perag in memory for the duration of the operation that is operating on the perag (e.g. transaction scope). This means we can fail to get an active reference to an AG, hence callers of the new active reference API must be able to handle lookup failure gracefully. Passive references are used in low level code, where we might need to access the perag structure for the purposes of completing high level operations. For example, buffers need to use passive references because: - we need to be able to do metadata IO during operations like grow and shrink transactions where high level active references to the AG have already been blocked - buffers need to pin the perag until they are reclaimed from memory, something that high level code has no direct control over. - unused cached buffers should not prevent a shrink from being started. Hence we have active references that will form exclusion barriers for operations to be performed on an AG, and passive references that will prevent reclaim of the perag until all objects with passive references have been reclaimed themselves. This patch introduce xfs_perag_grab()/xfs_perag_rele() as the API for active AG reference functionality. We also need to convert the for_each_perag*() iterators to use active references, which will start the process of converting high level code over to using active references. Conversion of non-iterator based code to active references will be done in followup patches. Note that the implementation using reference counting is really just a development vehicle for the API to ensure we don't have any leaks in the callers. Once we need to remove perag structures from memory dyanmically, we will need a much more robust per-ag state transition mechanism for preventing new references from being taken while we wait for existing references to drain before removal from memory can occur.... Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Allison Henderson <allison.henderson@oracle.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2023-02-12 22:14:42 +00:00
xfs_perag_rele(pag);
if (polled)
xfs_pwork_poll(&pctl);
return xfs_pwork_destroy(&pctl);
}
/*
* Allow callers to cache up to a page's worth of inobt records. This reflects
* the existing inumbers prefetching behavior. Since the inobt walk does not
* itself do anything with the inobt records, we can set a fairly high limit
* here.
*/
#define MAX_INOBT_WALK_PREFETCH \
(PAGE_SIZE / sizeof(struct xfs_inobt_rec_incore))
/*
* Given the number of records that the user wanted, set the number of inobt
* records that we buffer in memory. Set the maximum if @inobt_records == 0.
*/
static inline unsigned int
xfs_inobt_walk_prefetch(
unsigned int inobt_records)
{
/*
* If the caller didn't tell us the number of inobt records they
* wanted, assume the maximum prefetch possible for best performance.
*/
if (inobt_records == 0)
inobt_records = MAX_INOBT_WALK_PREFETCH;
/*
* 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.
*/
inobt_records = max(inobt_records, 2U);
/*
* Cap prefetch at that maximum so that we don't use an absurd amount
* of memory.
*/
return min_t(unsigned int, inobt_records, MAX_INOBT_WALK_PREFETCH);
}
/*
* Walk all inode btree records in the filesystem starting from @startino. The
* @inobt_walk_fn will be called for each btree record, being passed the incore
* record and @data. @max_prefetch controls how many inobt records we try to
* cache ahead of time.
*/
int
xfs_inobt_walk(
struct xfs_mount *mp,
struct xfs_trans *tp,
xfs_ino_t startino,
unsigned int flags,
xfs_inobt_walk_fn inobt_walk_fn,
unsigned int inobt_records,
void *data)
{
struct xfs_iwalk_ag iwag = {
.mp = mp,
.tp = tp,
.inobt_walk_fn = inobt_walk_fn,
.data = data,
.startino = startino,
.sz_recs = xfs_inobt_walk_prefetch(inobt_records),
.pwork = XFS_PWORK_SINGLE_THREADED,
.lastino = NULLFSINO,
};
struct xfs_perag *pag;
xfs_agnumber_t agno = XFS_INO_TO_AGNO(mp, startino);
int error;
ASSERT(agno < mp->m_sb.sb_agcount);
ASSERT(!(flags & ~XFS_INOBT_WALK_FLAGS_ALL));
error = xfs_iwalk_alloc(&iwag);
if (error)
return error;
for_each_perag_from(mp, agno, pag) {
iwag.pag = pag;
error = xfs_iwalk_ag(&iwag);
if (error)
break;
iwag.startino = XFS_AGINO_TO_INO(mp, pag->pag_agno + 1, 0);
if (flags & XFS_INOBT_WALK_SAME_AG)
break;
iwag.pag = NULL;
}
if (iwag.pag)
xfs: active perag reference counting We need to be able to dynamically remove instantiated AGs from memory safely, either for shrinking the filesystem or paging AG state in and out of memory (e.g. supporting millions of AGs). This means we need to be able to safely exclude operations from accessing perags while dynamic removal is in progress. To do this, introduce the concept of active and passive references. Active references are required for high level operations that make use of an AG for a given operation (e.g. allocation) and pin the perag in memory for the duration of the operation that is operating on the perag (e.g. transaction scope). This means we can fail to get an active reference to an AG, hence callers of the new active reference API must be able to handle lookup failure gracefully. Passive references are used in low level code, where we might need to access the perag structure for the purposes of completing high level operations. For example, buffers need to use passive references because: - we need to be able to do metadata IO during operations like grow and shrink transactions where high level active references to the AG have already been blocked - buffers need to pin the perag until they are reclaimed from memory, something that high level code has no direct control over. - unused cached buffers should not prevent a shrink from being started. Hence we have active references that will form exclusion barriers for operations to be performed on an AG, and passive references that will prevent reclaim of the perag until all objects with passive references have been reclaimed themselves. This patch introduce xfs_perag_grab()/xfs_perag_rele() as the API for active AG reference functionality. We also need to convert the for_each_perag*() iterators to use active references, which will start the process of converting high level code over to using active references. Conversion of non-iterator based code to active references will be done in followup patches. Note that the implementation using reference counting is really just a development vehicle for the API to ensure we don't have any leaks in the callers. Once we need to remove perag structures from memory dyanmically, we will need a much more robust per-ag state transition mechanism for preventing new references from being taken while we wait for existing references to drain before removal from memory can occur.... Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Allison Henderson <allison.henderson@oracle.com> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
2023-02-12 22:14:42 +00:00
xfs_perag_rele(pag);
xfs_iwalk_free(&iwag);
return error;
}