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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/xfs/xfs_discard.c
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/xfs/xfs_discard.c')
-rw-r--r--fs/xfs/xfs_discard.c432
1 files changed, 432 insertions, 0 deletions
diff --git a/fs/xfs/xfs_discard.c b/fs/xfs/xfs_discard.c
new file mode 100644
index 0000000000..d5787991bb
--- /dev/null
+++ b/fs/xfs/xfs_discard.c
@@ -0,0 +1,432 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2010, 2023 Red Hat, Inc.
+ * All Rights Reserved.
+ */
+#include "xfs.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_btree.h"
+#include "xfs_alloc_btree.h"
+#include "xfs_alloc.h"
+#include "xfs_discard.h"
+#include "xfs_error.h"
+#include "xfs_extent_busy.h"
+#include "xfs_trace.h"
+#include "xfs_log.h"
+#include "xfs_ag.h"
+
+/*
+ * Notes on an efficient, low latency fstrim algorithm
+ *
+ * We need to walk the filesystem free space and issue discards on the free
+ * space that meet the search criteria (size and location). We cannot issue
+ * discards on extents that might be in use, or are so recently in use they are
+ * still marked as busy. To serialise against extent state changes whilst we are
+ * gathering extents to trim, we must hold the AGF lock to lock out other
+ * allocations and extent free operations that might change extent state.
+ *
+ * However, we cannot just hold the AGF for the entire AG free space walk whilst
+ * we issue discards on each free space that is found. Storage devices can have
+ * extremely slow discard implementations (e.g. ceph RBD) and so walking a
+ * couple of million free extents and issuing synchronous discards on each
+ * extent can take a *long* time. Whilst we are doing this walk, nothing else
+ * can access the AGF, and we can stall transactions and hence the log whilst
+ * modifications wait for the AGF lock to be released. This can lead hung tasks
+ * kicking the hung task timer and rebooting the system. This is bad.
+ *
+ * Hence we need to take a leaf from the bulkstat playbook. It takes the AGI
+ * lock, gathers a range of inode cluster buffers that are allocated, drops the
+ * AGI lock and then reads all the inode cluster buffers and processes them. It
+ * loops doing this, using a cursor to keep track of where it is up to in the AG
+ * for each iteration to restart the INOBT lookup from.
+ *
+ * We can't do this exactly with free space - once we drop the AGF lock, the
+ * state of the free extent is out of our control and we cannot run a discard
+ * safely on it in this situation. Unless, of course, we've marked the free
+ * extent as busy and undergoing a discard operation whilst we held the AGF
+ * locked.
+ *
+ * This is exactly how online discard works - free extents are marked busy when
+ * they are freed, and once the extent free has been committed to the journal,
+ * the busy extent record is marked as "undergoing discard" and the discard is
+ * then issued on the free extent. Once the discard completes, the busy extent
+ * record is removed and the extent is able to be allocated again.
+ *
+ * In the context of fstrim, if we find a free extent we need to discard, we
+ * don't have to discard it immediately. All we need to do it record that free
+ * extent as being busy and under discard, and all the allocation routines will
+ * now avoid trying to allocate it. Hence if we mark the extent as busy under
+ * the AGF lock, we can safely discard it without holding the AGF lock because
+ * nothing will attempt to allocate that free space until the discard completes.
+ *
+ * This also allows us to issue discards asynchronously like we do with online
+ * discard, and so for fast devices fstrim will run much faster as we can have
+ * multiple discard operations in flight at once, as well as pipeline the free
+ * extent search so that it overlaps in flight discard IO.
+ */
+
+struct workqueue_struct *xfs_discard_wq;
+
+static void
+xfs_discard_endio_work(
+ struct work_struct *work)
+{
+ struct xfs_busy_extents *extents =
+ container_of(work, struct xfs_busy_extents, endio_work);
+
+ xfs_extent_busy_clear(extents->mount, &extents->extent_list, false);
+ kmem_free(extents->owner);
+}
+
+/*
+ * Queue up the actual completion to a thread to avoid IRQ-safe locking for
+ * pagb_lock.
+ */
+static void
+xfs_discard_endio(
+ struct bio *bio)
+{
+ struct xfs_busy_extents *extents = bio->bi_private;
+
+ INIT_WORK(&extents->endio_work, xfs_discard_endio_work);
+ queue_work(xfs_discard_wq, &extents->endio_work);
+ bio_put(bio);
+}
+
+/*
+ * Walk the discard list and issue discards on all the busy extents in the
+ * list. We plug and chain the bios so that we only need a single completion
+ * call to clear all the busy extents once the discards are complete.
+ */
+int
+xfs_discard_extents(
+ struct xfs_mount *mp,
+ struct xfs_busy_extents *extents)
+{
+ struct xfs_extent_busy *busyp;
+ struct bio *bio = NULL;
+ struct blk_plug plug;
+ int error = 0;
+
+ blk_start_plug(&plug);
+ list_for_each_entry(busyp, &extents->extent_list, list) {
+ trace_xfs_discard_extent(mp, busyp->agno, busyp->bno,
+ busyp->length);
+
+ error = __blkdev_issue_discard(mp->m_ddev_targp->bt_bdev,
+ XFS_AGB_TO_DADDR(mp, busyp->agno, busyp->bno),
+ XFS_FSB_TO_BB(mp, busyp->length),
+ GFP_NOFS, &bio);
+ if (error && error != -EOPNOTSUPP) {
+ xfs_info(mp,
+ "discard failed for extent [0x%llx,%u], error %d",
+ (unsigned long long)busyp->bno,
+ busyp->length,
+ error);
+ break;
+ }
+ }
+
+ if (bio) {
+ bio->bi_private = extents;
+ bio->bi_end_io = xfs_discard_endio;
+ submit_bio(bio);
+ } else {
+ xfs_discard_endio_work(&extents->endio_work);
+ }
+ blk_finish_plug(&plug);
+
+ return error;
+}
+
+
+static int
+xfs_trim_gather_extents(
+ struct xfs_perag *pag,
+ xfs_daddr_t start,
+ xfs_daddr_t end,
+ xfs_daddr_t minlen,
+ struct xfs_alloc_rec_incore *tcur,
+ struct xfs_busy_extents *extents,
+ uint64_t *blocks_trimmed)
+{
+ struct xfs_mount *mp = pag->pag_mount;
+ struct xfs_btree_cur *cur;
+ struct xfs_buf *agbp;
+ int error;
+ int i;
+ int batch = 100;
+
+ /*
+ * Force out the log. This means any transactions that might have freed
+ * space before we take the AGF buffer lock are now on disk, and the
+ * volatile disk cache is flushed.
+ */
+ xfs_log_force(mp, XFS_LOG_SYNC);
+
+ error = xfs_alloc_read_agf(pag, NULL, 0, &agbp);
+ if (error)
+ return error;
+
+ cur = xfs_allocbt_init_cursor(mp, NULL, agbp, pag, XFS_BTNUM_CNT);
+
+ /*
+ * Look up the extent length requested in the AGF and start with it.
+ */
+ if (tcur->ar_startblock == NULLAGBLOCK)
+ error = xfs_alloc_lookup_ge(cur, 0, tcur->ar_blockcount, &i);
+ else
+ error = xfs_alloc_lookup_le(cur, tcur->ar_startblock,
+ tcur->ar_blockcount, &i);
+ if (error)
+ goto out_del_cursor;
+ if (i == 0) {
+ /* nothing of that length left in the AG, we are done */
+ tcur->ar_blockcount = 0;
+ goto out_del_cursor;
+ }
+
+ /*
+ * Loop until we are done with all extents that are large
+ * enough to be worth discarding or we hit batch limits.
+ */
+ while (i) {
+ xfs_agblock_t fbno;
+ xfs_extlen_t flen;
+ xfs_daddr_t dbno;
+ xfs_extlen_t dlen;
+
+ error = xfs_alloc_get_rec(cur, &fbno, &flen, &i);
+ if (error)
+ break;
+ if (XFS_IS_CORRUPT(mp, i != 1)) {
+ error = -EFSCORRUPTED;
+ break;
+ }
+
+ if (--batch <= 0) {
+ /*
+ * Update the cursor to point at this extent so we
+ * restart the next batch from this extent.
+ */
+ tcur->ar_startblock = fbno;
+ tcur->ar_blockcount = flen;
+ break;
+ }
+
+ /*
+ * use daddr format for all range/len calculations as that is
+ * the format the range/len variables are supplied in by
+ * userspace.
+ */
+ dbno = XFS_AGB_TO_DADDR(mp, pag->pag_agno, fbno);
+ dlen = XFS_FSB_TO_BB(mp, flen);
+
+ /*
+ * Too small? Give up.
+ */
+ if (dlen < minlen) {
+ trace_xfs_discard_toosmall(mp, pag->pag_agno, fbno, flen);
+ tcur->ar_blockcount = 0;
+ break;
+ }
+
+ /*
+ * If the extent is entirely outside of the range we are
+ * supposed to discard skip it. Do not bother to trim
+ * down partially overlapping ranges for now.
+ */
+ if (dbno + dlen < start || dbno > end) {
+ trace_xfs_discard_exclude(mp, pag->pag_agno, fbno, flen);
+ goto next_extent;
+ }
+
+ /*
+ * If any blocks in the range are still busy, skip the
+ * discard and try again the next time.
+ */
+ if (xfs_extent_busy_search(mp, pag, fbno, flen)) {
+ trace_xfs_discard_busy(mp, pag->pag_agno, fbno, flen);
+ goto next_extent;
+ }
+
+ xfs_extent_busy_insert_discard(pag, fbno, flen,
+ &extents->extent_list);
+ *blocks_trimmed += flen;
+next_extent:
+ error = xfs_btree_decrement(cur, 0, &i);
+ if (error)
+ break;
+
+ /*
+ * If there's no more records in the tree, we are done. Set the
+ * cursor block count to 0 to indicate to the caller that there
+ * is no more extents to search.
+ */
+ if (i == 0)
+ tcur->ar_blockcount = 0;
+ }
+
+ /*
+ * If there was an error, release all the gathered busy extents because
+ * we aren't going to issue a discard on them any more.
+ */
+ if (error)
+ xfs_extent_busy_clear(mp, &extents->extent_list, false);
+out_del_cursor:
+ xfs_btree_del_cursor(cur, error);
+ xfs_buf_relse(agbp);
+ return error;
+}
+
+static bool
+xfs_trim_should_stop(void)
+{
+ return fatal_signal_pending(current) || freezing(current);
+}
+
+/*
+ * Iterate the free list gathering extents and discarding them. We need a cursor
+ * for the repeated iteration of gather/discard loop, so use the longest extent
+ * we found in the last batch as the key to start the next.
+ */
+static int
+xfs_trim_extents(
+ struct xfs_perag *pag,
+ xfs_daddr_t start,
+ xfs_daddr_t end,
+ xfs_daddr_t minlen,
+ uint64_t *blocks_trimmed)
+{
+ struct xfs_alloc_rec_incore tcur = {
+ .ar_blockcount = pag->pagf_longest,
+ .ar_startblock = NULLAGBLOCK,
+ };
+ int error = 0;
+
+ do {
+ struct xfs_busy_extents *extents;
+
+ extents = kzalloc(sizeof(*extents), GFP_KERNEL);
+ if (!extents) {
+ error = -ENOMEM;
+ break;
+ }
+
+ extents->mount = pag->pag_mount;
+ extents->owner = extents;
+ INIT_LIST_HEAD(&extents->extent_list);
+
+ error = xfs_trim_gather_extents(pag, start, end, minlen,
+ &tcur, extents, blocks_trimmed);
+ if (error) {
+ kfree(extents);
+ break;
+ }
+
+ /*
+ * We hand the extent list to the discard function here so the
+ * discarded extents can be removed from the busy extent list.
+ * This allows the discards to run asynchronously with gathering
+ * the next round of extents to discard.
+ *
+ * However, we must ensure that we do not reference the extent
+ * list after this function call, as it may have been freed by
+ * the time control returns to us.
+ */
+ error = xfs_discard_extents(pag->pag_mount, extents);
+ if (error)
+ break;
+
+ if (xfs_trim_should_stop())
+ break;
+
+ } while (tcur.ar_blockcount != 0);
+
+ return error;
+
+}
+
+/*
+ * trim a range of the filesystem.
+ *
+ * Note: the parameters passed from userspace are byte ranges into the
+ * filesystem which does not match to the format we use for filesystem block
+ * addressing. FSB addressing is sparse (AGNO|AGBNO), while the incoming format
+ * is a linear address range. Hence we need to use DADDR based conversions and
+ * comparisons for determining the correct offset and regions to trim.
+ */
+int
+xfs_ioc_trim(
+ struct xfs_mount *mp,
+ struct fstrim_range __user *urange)
+{
+ struct xfs_perag *pag;
+ unsigned int granularity =
+ bdev_discard_granularity(mp->m_ddev_targp->bt_bdev);
+ struct fstrim_range range;
+ xfs_daddr_t start, end, minlen;
+ xfs_agnumber_t agno;
+ uint64_t blocks_trimmed = 0;
+ int error, last_error = 0;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ if (!bdev_max_discard_sectors(mp->m_ddev_targp->bt_bdev))
+ return -EOPNOTSUPP;
+
+ /*
+ * We haven't recovered the log, so we cannot use our bnobt-guided
+ * storage zapping commands.
+ */
+ if (xfs_has_norecovery(mp))
+ return -EROFS;
+
+ if (copy_from_user(&range, urange, sizeof(range)))
+ return -EFAULT;
+
+ range.minlen = max_t(u64, granularity, range.minlen);
+ minlen = BTOBB(range.minlen);
+ /*
+ * Truncating down the len isn't actually quite correct, but using
+ * BBTOB would mean we trivially get overflows for values
+ * of ULLONG_MAX or slightly lower. And ULLONG_MAX is the default
+ * used by the fstrim application. In the end it really doesn't
+ * matter as trimming blocks is an advisory interface.
+ */
+ if (range.start >= XFS_FSB_TO_B(mp, mp->m_sb.sb_dblocks) ||
+ range.minlen > XFS_FSB_TO_B(mp, mp->m_ag_max_usable) ||
+ range.len < mp->m_sb.sb_blocksize)
+ return -EINVAL;
+
+ start = BTOBB(range.start);
+ end = start + BTOBBT(range.len) - 1;
+
+ if (end > XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1)
+ end = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks) - 1;
+
+ agno = xfs_daddr_to_agno(mp, start);
+ for_each_perag_range(mp, agno, xfs_daddr_to_agno(mp, end), pag) {
+ error = xfs_trim_extents(pag, start, end, minlen,
+ &blocks_trimmed);
+ if (error)
+ last_error = error;
+
+ if (xfs_trim_should_stop()) {
+ xfs_perag_rele(pag);
+ break;
+ }
+ }
+
+ if (last_error)
+ return last_error;
+
+ range.len = XFS_FSB_TO_B(mp, blocks_trimmed);
+ if (copy_to_user(urange, &range, sizeof(range)))
+ return -EFAULT;
+ return 0;
+}