[PATCH 4/4] xfs: add the ability to reap entire inode forks

Darrick J. Wong
2023-12-31T20:31:49Z

In preparation for supporting repair of indexed file-based metadata
(such as realtime bitmaps, directories, and extended attribute data),
add a function to reap the old blocks after a metadata repair finishes.
IOWs, this is an elaborate bunmapi call that deals with crosslinked
blocks by unmapping them without freeing them, and also scans for incore
buffers to invalidate.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/scrub/reap.c | 372 ++++++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/scrub/reap.h | 1
fs/xfs/scrub/trace.h | 63 ++++++++
3 files changed, 436 insertions(+)

diff --git a/fs/xfs/scrub/reap.c b/fs/xfs/scrub/reap.c
index 7ae6253395e72..01ceaa4efa16b 100644
--- a/fs/xfs/scrub/reap.c
+++ b/fs/xfs/scrub/reap.c
@@ -675,3 +675,375 @@ xrep_reap_fsblocks(

return 0;
}
+
+/*
+ * Metadata files are not supposed to share blocks with anything else.
+ * If blocks are shared, we remove the reverse mapping (thus reducing the
+ * crosslink factor); if blocks are not shared, we also need to free them.
+ *
+ * This first step determines the longest subset of the passed-in imap
+ * (starting at its beginning) that is either crosslinked or not crosslinked.
+ * The blockcount will be adjust down as needed.
+ */
+STATIC int
+xreap_bmapi_select(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ int whichfork,
+ struct xfs_bmbt_irec *imap,
+ bool *crosslinked)
+{
+ struct xfs_owner_info oinfo;
+ struct xfs_btree_cur *cur;
+ xfs_filblks_t len = 1;
+ xfs_agblock_t bno;
+ xfs_agblock_t agbno;
+ xfs_agblock_t agbno_next;
+ int error;
+
+ agbno = XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock);
+ agbno_next = agbno + imap->br_blockcount;
+
+ cur = xfs_rmapbt_init_cursor(sc->mp, sc->tp, sc->sa.agf_bp,
+ sc->sa.pag);
+
+ xfs_rmap_ino_owner(&oinfo, ip->i_ino, whichfork, imap->br_startoff);
+ error = xfs_rmap_has_other_keys(cur, agbno, 1, &oinfo, crosslinked);
+ if (error)
+ goto out_cur;
+
+ bno = agbno + 1;
+ while (bno < agbno_next) {
+ bool also_crosslinked;
+
+ oinfo.oi_offset++;
+ error = xfs_rmap_has_other_keys(cur, bno, 1, &oinfo,
+ &also_crosslinked);
+ if (error)
+ goto out_cur;
+
+ if (also_crosslinked != *crosslinked)
+ break;
+
+ len++;
+ bno++;
+ }
+
+ imap->br_blockcount = len;
+ trace_xreap_bmapi_select(sc->sa.pag, agbno, len, *crosslinked);
+out_cur:
+ xfs_btree_del_cursor(cur, error);
+ return error;
+}
+
+/*
+ * Decide if this buffer can be joined to a transaction. This is true for most
+ * buffers, but there are two cases that we want to catch: large remote xattr
+ * value buffers are not logged and can overflow the buffer log item dirty
+ * bitmap size; and oversized cached buffers if things have really gone
+ * haywire.
+ */
+static inline bool
+xreap_buf_loggable(
+ const struct xfs_buf *bp)
+{
+ int i;
+
+ for (i = 0; i < bp->b_map_count; i++) {
+ int chunks;
+ int map_size;
+
+ chunks = DIV_ROUND_UP(BBTOB(bp->b_maps[i].bm_len),
+ XFS_BLF_CHUNK);
+ map_size = DIV_ROUND_UP(chunks, NBWORD);
+ if (map_size > XFS_BLF_DATAMAP_SIZE)
+ return false;
+ }
+
+ return true;
+}
+
+/*
+ * Invalidate any buffers for this file mapping. The @imap blockcount may be
+ * adjusted downward if we need to roll the transaction.
+ */
+STATIC int
+xreap_bmapi_binval(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ int whichfork,
+ struct xfs_bmbt_irec *imap)
+{
+ struct xfs_mount *mp = sc->mp;
+ struct xfs_perag *pag = sc->sa.pag;
+ int bmap_flags = xfs_bmapi_aflag(whichfork);
+ xfs_fileoff_t off;
+ xfs_fileoff_t max_off;
+ xfs_extlen_t scan_blocks;
+ xfs_agnumber_t agno = sc->sa.pag->pag_agno;
+ xfs_agblock_t bno;
+ xfs_agblock_t agbno;
+ xfs_agblock_t agbno_next;
+ unsigned int invalidated = 0;
+ int error;
+
+ /*
+ * Avoid invalidating AG headers and post-EOFS blocks because we never
+ * own those.
+ */
+ agbno = bno = XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock);
+ agbno_next = agbno + imap->br_blockcount;
+ if (!xfs_verify_agbno(pag, agbno) ||
+ !xfs_verify_agbno(pag, agbno_next - 1))
+ return 0;
+
+ /*
+ * Buffers for file blocks can span multiple contiguous mappings. This
+ * means that for each block in the mapping, there could exist an
+ * xfs_buf indexed by that block with any length up to the maximum
+ * buffer size (remote xattr values) or to the next hole in the fork.
+ * To set up our binval scan, first we need to figure out the location
+ * of the next hole.
+ */
+ off = imap->br_startoff + imap->br_blockcount;
+ max_off = off + xfs_attr3_rmt_blocks(mp, XFS_XATTR_SIZE_MAX);
+ while (off < max_off) {
+ struct xfs_bmbt_irec hmap;
+ int nhmaps = 1;
+
+ error = xfs_bmapi_read(ip, off, max_off - off, &hmap,
+ &nhmaps, bmap_flags);
+ if (error)
+ return error;
+ if (nhmaps != 1 || hmap.br_startblock == DELAYSTARTBLOCK) {
+ ASSERT(0);
+ return -EFSCORRUPTED;
+ }
+
+ if (!xfs_bmap_is_real_extent(&hmap))
+ break;
+
+ off = hmap.br_startoff + hmap.br_blockcount;
+ }
+ scan_blocks = off - imap->br_startoff;
+
+ trace_xreap_bmapi_binval_scan(sc, imap, scan_blocks);
+
+ /*
+ * If there are incore buffers for these blocks, invalidate them. If
+ * we can't (try)lock the buffer we assume it's owned by someone else
+ * and leave it alone. The buffer cache cannot detect aliasing, so
+ * employ nested loops to detect incore buffers of any plausible size.
+ */
+ while (bno < agbno_next) {
+ struct xrep_bufscan scan = {
+ .daddr = XFS_AGB_TO_DADDR(mp, agno, bno),
+ .max_sectors = xrep_bufscan_max_sectors(mp,
+ scan_blocks),
+ .daddr_step = XFS_FSB_TO_BB(mp, 1),
+ };
+ struct xfs_buf *bp;
+
+ while ((bp = xrep_bufscan_advance(mp, &scan)) != NULL) {
+ if (xreap_buf_loggable(bp)) {
+ xfs_trans_bjoin(sc->tp, bp);
+ xfs_trans_binval(sc->tp, bp);
+ } else {
+ xfs_buf_stale(bp);
+ xfs_buf_relse(bp);
+ }
+ invalidated++;
+
+ /*
+ * Stop invalidating if we've hit the limit; we should
+ * still have enough reservation left to free however
+ * much of the mapping we've seen so far.
+ */
+ if (invalidated > XREAP_MAX_BINVAL) {
+ imap->br_blockcount = agbno_next - bno;
+ goto out;
+ }
+ }
+
+ bno++;
+ scan_blocks--;
+ }
+
+out:
+ trace_xreap_bmapi_binval(sc->sa.pag, agbno, imap->br_blockcount);
+ return 0;
+}
+
+/*
+ * Dispose of as much of the beginning of this file fork mapping as possible.
+ * The number of blocks disposed of is returned in @imap->br_blockcount.
+ */
+STATIC int
+xrep_reap_bmapi_iter(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ int whichfork,
+ struct xfs_bmbt_irec *imap,
+ bool crosslinked)
+{
+ int error;
+
+ if (crosslinked) {
+ /*
+ * If there are other rmappings, this block is cross linked and
+ * must not be freed. Remove the reverse mapping, leave the
+ * buffer cache in its possibly confused state, and move on.
+ * We don't want to risk discarding valid data buffers from
+ * anybody else who thinks they own the block, even though that
+ * runs the risk of stale buffer warnings in the future.
+ */
+ trace_xreap_dispose_unmap_extent(sc->sa.pag,
+ XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock),
+ imap->br_blockcount);
+
+ /*
+ * Schedule removal of the mapping from the fork. We use
+ * deferred log intents in this function to control the exact
+ * sequence of metadata updates.
+ */
+ xfs_bmap_unmap_extent(sc->tp, ip, whichfork, imap);
+ xfs_trans_mod_dquot_byino(sc->tp, ip, XFS_TRANS_DQ_BCOUNT,
+ -(int64_t)imap->br_blockcount);
+ xfs_rmap_unmap_extent(sc->tp, ip, whichfork, imap);
+ return 0;
+ }
+
+ /*
+ * If the block is not crosslinked, we can invalidate all the incore
+ * buffers for the extent, and then free the extent. This is a bit of
+ * a mess since we don't detect discontiguous buffers that are indexed
+ * by a block starting before the first block of the extent but overlap
+ * anyway.
+ */
+ trace_xreap_dispose_free_extent(sc->sa.pag,
+ XFS_FSB_TO_AGBNO(sc->mp, imap->br_startblock),
+ imap->br_blockcount);
+
+ /*
+ * Invalidate as many buffers as we can, starting at the beginning of
+ * this mapping. If this function sets blockcount to zero, the
+ * transaction is full of logged buffer invalidations, so we need to
+ * return early so that we can roll and retry.
+ */
+ error = xreap_bmapi_binval(sc, ip, whichfork, imap);
+ if (error || imap->br_blockcount == 0)
+ return error;
+
+ /*
+ * Schedule removal of the mapping from the fork. We use deferred log
+ * intents in this function to control the exact sequence of metadata
+ * updates.
+ */
+ xfs_bmap_unmap_extent(sc->tp, ip, whichfork, imap);
+ xfs_trans_mod_dquot_byino(sc->tp, ip, XFS_TRANS_DQ_BCOUNT,
+ -(int64_t)imap->br_blockcount);
+ return xfs_free_extent_later(sc->tp, imap->br_startblock,
+ imap->br_blockcount, NULL, XFS_AG_RESV_NONE, true);
+}
+
+/*
+ * Dispose of as much of this file extent as we can. Upon successful return,
+ * the imap will reflect the mapping that was removed from the fork.
+ */
+STATIC int
+xreap_ifork_extent(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ int whichfork,
+ struct xfs_bmbt_irec *imap)
+{
+ xfs_agnumber_t agno;
+ bool crosslinked;
+ int error;
+
+ ASSERT(sc->sa.pag == NULL);
+
+ trace_xreap_ifork_extent(sc, ip, whichfork, imap);
+
+ agno = XFS_FSB_TO_AGNO(sc->mp, imap->br_startblock);
+ sc->sa.pag = xfs_perag_get(sc->mp, agno);
+ if (!sc->sa.pag)
+ return -EFSCORRUPTED;
+
+ error = xfs_alloc_read_agf(sc->sa.pag, sc->tp, 0, &sc->sa.agf_bp);
+ if (error)
+ goto out_pag;
+
+ /*
+ * Decide the fate of the blocks at the beginning of the mapping, then
+ * update the mapping to use it with the unmap calls.
+ */
+ error = xreap_bmapi_select(sc, ip, whichfork, imap, &crosslinked);
+ if (error)
+ goto out_agf;
+
+ error = xrep_reap_bmapi_iter(sc, ip, whichfork, imap, crosslinked);
+ if (error)
+ goto out_agf;
+
+out_agf:
+ xfs_trans_brelse(sc->tp, sc->sa.agf_bp);
+ sc->sa.agf_bp = NULL;
+out_pag:
+ xfs_perag_put(sc->sa.pag);
+ sc->sa.pag = NULL;
+ return error;
+}
+
+/*
+ * Dispose of each block mapped to the given fork of the given file. Callers
+ * must hold ILOCK_EXCL, and ip can only be sc->ip or sc->tempip. The fork
+ * must not have any delalloc reservations.
+ */
+int
+xrep_reap_ifork(
+ struct xfs_scrub *sc,
+ struct xfs_inode *ip,
+ int whichfork)
+{
+ xfs_fileoff_t off = 0;
+ int bmap_flags = xfs_bmapi_aflag(whichfork);
+ int error;
+
+ ASSERT(xfs_has_rmapbt(sc->mp));
+ ASSERT(ip == sc->ip || ip == sc->tempip);
+ ASSERT(whichfork == XFS_ATTR_FORK || !XFS_IS_REALTIME_INODE(ip));
+
+ while (off < XFS_MAX_FILEOFF) {
+ struct xfs_bmbt_irec imap;
+ int nimaps = 1;
+
+ /* Read the next extent, skip past holes and delalloc. */
+ error = xfs_bmapi_read(ip, off, XFS_MAX_FILEOFF - off, &imap,
+ &nimaps, bmap_flags);
+ if (error)
+ return error;
+ if (nimaps != 1 || imap.br_startblock == DELAYSTARTBLOCK) {
+ ASSERT(0);
+ return -EFSCORRUPTED;
+ }
+
+ /*
+ * If this is a real space mapping, reap as much of it as we
+ * can in a single transaction.
+ */
+ if (xfs_bmap_is_real_extent(&imap)) {
+ error = xreap_ifork_extent(sc, ip, whichfork, &imap);
+ if (error)
+ return error;
+
+ error = xfs_defer_finish(&sc->tp);
+ if (error)
+ return error;
+ }
+
+ off = imap.br_startoff + imap.br_blockcount;
+ }
+
+ return 0;
+}
diff --git a/fs/xfs/scrub/reap.h b/fs/xfs/scrub/reap.h
index bb09e21fcb172..3f2f1775e29db 100644
--- a/fs/xfs/scrub/reap.h
+++ b/fs/xfs/scrub/reap.h
@@ -13,6 +13,7 @@ int xrep_reap_agblocks(struct xfs_scrub *sc, struct xagb_bitmap *bitmap,
const struct xfs_owner_info *oinfo, enum xfs_ag_resv_type type);
int xrep_reap_fsblocks(struct xfs_scrub *sc, struct xfsb_bitmap *bitmap,
const struct xfs_owner_info *oinfo);
+int xrep_reap_ifork(struct xfs_scrub *sc, struct xfs_inode *ip, int whichfork);

/* Buffer cache scan context. */
struct xrep_bufscan {
diff --git a/fs/xfs/scrub/trace.h b/fs/xfs/scrub/trace.h
index 00f906e50c341..691c91c9a5853 100644
--- a/fs/xfs/scrub/trace.h
+++ b/fs/xfs/scrub/trace.h
@@ -1510,6 +1510,7 @@ DEFINE_EVENT(xrep_extent_class, name, \
DEFINE_REPAIR_EXTENT_EVENT(xreap_dispose_unmap_extent);
DEFINE_REPAIR_EXTENT_EVENT(xreap_dispose_free_extent);
DEFINE_REPAIR_EXTENT_EVENT(xreap_agextent_binval);
+DEFINE_REPAIR_EXTENT_EVENT(xreap_bmapi_binval);
DEFINE_REPAIR_EXTENT_EVENT(xrep_agfl_insert);

DECLARE_EVENT_CLASS(xrep_reap_find_class,
@@ -1543,6 +1544,7 @@ DEFINE_EVENT(xrep_reap_find_class, name, \
bool crosslinked), \
TP_ARGS(pag, agbno, len, crosslinked))
DEFINE_REPAIR_REAP_FIND_EVENT(xreap_agextent_select);
+DEFINE_REPAIR_REAP_FIND_EVENT(xreap_bmapi_select);

DECLARE_EVENT_CLASS(xrep_rmap_class,
TP_PROTO(struct xfs_mount *mp, xfs_agnumber_t agno,
@@ -2394,6 +2396,67 @@ TRACE_EVENT(xrep_tempfile_create,
__entry->temp_inum)
);

+TRACE_EVENT(xreap_ifork_extent,
+ TP_PROTO(struct xfs_scrub *sc, struct xfs_inode *ip, int whichfork,
+ const struct xfs_bmbt_irec *irec),
+ TP_ARGS(sc, ip, whichfork, irec),
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(xfs_ino_t, ino)
+ __field(int, whichfork)
+ __field(xfs_fileoff_t, fileoff)
+ __field(xfs_filblks_t, len)
+ __field(xfs_agnumber_t, agno)
+ __field(xfs_agblock_t, agbno)
+ __field(int, state)
+ ),
+ TP_fast_assign(
+ __entry->dev = sc->mp->m_super->s_dev;
+ __entry->ino = ip->i_ino;
+ __entry->whichfork = whichfork;
+ __entry->fileoff = irec->br_startoff;
+ __entry->len = irec->br_blockcount;
+ __entry->agno = XFS_FSB_TO_AGNO(sc->mp, irec->br_startblock);
+ __entry->agbno = XFS_FSB_TO_AGBNO(sc->mp, irec->br_startblock);
+ __entry->state = irec->br_state;
+ ),
+ TP_printk("dev %d:%d ip 0x%llx whichfork %s agno 0x%x agbno 0x%x fileoff 0x%llx fsbcount 0x%llx state 0x%x",
+ MAJOR(__entry->dev), MINOR(__entry->dev),
+ __entry->ino,
+ __print_symbolic(__entry->whichfork, XFS_WHICHFORK_STRINGS),
+ __entry->agno,
+ __entry->agbno,
+ __entry->fileoff,
+ __entry->len,
+ __entry->state)
+);
+
+TRACE_EVENT(xreap_bmapi_binval_scan,
+ TP_PROTO(struct xfs_scrub *sc, const struct xfs_bmbt_irec *irec,
+ xfs_extlen_t scan_blocks),
+ TP_ARGS(sc, irec, scan_blocks),
+ TP_STRUCT__entry(
+ __field(dev_t, dev)
+ __field(xfs_filblks_t, len)
+ __field(xfs_agnumber_t, agno)
+ __field(xfs_agblock_t, agbno)
+ __field(xfs_extlen_t, scan_blocks)
+ ),
+ TP_fast_assign(
+ __entry->dev = sc->mp->m_super->s_dev;
+ __entry->len = irec->br_blockcount;
+ __entry->agno = XFS_FSB_TO_AGNO(sc->mp, irec->br_startblock);
+ __entry->agbno = XFS_FSB_TO_AGBNO(sc->mp, irec->br_startblock);
+ __entry->scan_blocks = scan_blocks;
+ ),
+ TP_printk("dev %d:%d agno 0x%x agbno 0x%x fsbcount 0x%llx scan_blocks 0x%x",
+ MAJOR(__entry->dev), MINOR(__entry->dev),
+ __entry->agno,
+ __entry->agbno,
+ __entry->len,
+ __entry->scan_blocks)
+);
+
#endif /* IS_ENABLED(CONFIG_XFS_ONLINE_REPAIR) */