[PATCH 2/8] xfs: use deferred frees for btree block freeing

Dave Chinner
2023-06-27T22:44:31Z

From: Dave Chinner <dchinner@redhat.com>

Btrees that aren't freespace management trees use the normal extent
allocation and freeing routines for their blocks. Hence when a btree
block is freed, a direct call to xfs_free_extent() is made and the
extent is immediately freed. This puts the entire free space
management btrees under this path, so we are stacking btrees on
btrees in the call stack. The inobt, finobt and refcount btrees
all do this.

However, the bmap btree does not do this - it calls
xfs_free_extent_later() to defer the extent free operation via an
XEFI and hence it gets processed in deferred operation processing
during the commit of the primary transaction (i.e. via intent
chaining).

We need to change xfs_free_extent() to behave in a non-blocking
manner so that we can avoid deadlocks with busy extents near ENOSPC
in transactions that free multiple extents. Inserting or removing a
record from a btree can cause a multi-level tree merge operation and
that will free multiple blocks from the btree in a single
transaction. i.e. we can call xfs_free_extent() multiple times, and
hence the btree manipulation transaction is vulnerable to this busy
extent deadlock vector.

To fix this, convert all the remaining callers of xfs_free_extent()
to use xfs_free_extent_later() to queue XEFIs and hence defer
processing of the extent frees to a context that can be safely
restarted if a deadlock condition is detected.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/libxfs/xfs_ag.c | 2 +-
fs/xfs/libxfs/xfs_alloc.c | 4 ++++
fs/xfs/libxfs/xfs_alloc.h | 8 +++++---
fs/xfs/libxfs/xfs_bmap.c | 8 +++++---
fs/xfs/libxfs/xfs_bmap_btree.c | 3 ++-
fs/xfs/libxfs/xfs_ialloc.c | 8 ++++----
fs/xfs/libxfs/xfs_ialloc_btree.c | 3 +--
fs/xfs/libxfs/xfs_refcount.c | 9 ++++++---
fs/xfs/libxfs/xfs_refcount_btree.c | 8 +-------
fs/xfs/xfs_extfree_item.c | 3 ++-
fs/xfs/xfs_reflink.c | 3 ++-
11 files changed, 33 insertions(+), 26 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_ag.c b/fs/xfs/libxfs/xfs_ag.c
index ee84835ebc66..e9cc481b4ddf 100644
--- a/fs/xfs/libxfs/xfs_ag.c
+++ b/fs/xfs/libxfs/xfs_ag.c
@@ -985,7 +985,7 @@ xfs_ag_shrink_space(
goto resv_err;

err2 = __xfs_free_extent_later(*tpp, args.fsbno, delta, NULL,
- true);
+ XFS_AG_RESV_NONE, true);
if (err2)
goto resv_err;

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index c20fe99405d8..cc3f7b905ea1 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2449,6 +2449,7 @@ xfs_defer_agfl_block(
xefi->xefi_startblock = XFS_AGB_TO_FSB(mp, agno, agbno);
xefi->xefi_blockcount = 1;
xefi->xefi_owner = oinfo->oi_owner;
+ xefi->xefi_type = XFS_AG_RESV_AGFL;

if (XFS_IS_CORRUPT(mp, !xfs_verify_fsbno(mp, xefi->xefi_startblock)))
return -EFSCORRUPTED;
@@ -2470,6 +2471,7 @@ __xfs_free_extent_later(
xfs_fsblock_t bno,
xfs_filblks_t len,
const struct xfs_owner_info *oinfo,
+ enum xfs_ag_resv_type type,
bool skip_discard)
{
struct xfs_extent_free_item *xefi;
@@ -2490,6 +2492,7 @@ __xfs_free_extent_later(
ASSERT(agbno + len <= mp->m_sb.sb_agblocks);
#endif
ASSERT(xfs_extfree_item_cache != NULL);
+ ASSERT(type != XFS_AG_RESV_AGFL);

if (XFS_IS_CORRUPT(mp, !xfs_verify_fsbext(mp, bno, len)))
return -EFSCORRUPTED;
@@ -2498,6 +2501,7 @@ __xfs_free_extent_later(
GFP_KERNEL | __GFP_NOFAIL);
xefi->xefi_startblock = bno;
xefi->xefi_blockcount = (xfs_extlen_t)len;
+ xefi->xefi_type = type;
if (skip_discard)
xefi->xefi_flags |= XFS_EFI_SKIP_DISCARD;
if (oinfo) {
diff --git a/fs/xfs/libxfs/xfs_alloc.h b/fs/xfs/libxfs/xfs_alloc.h
index 85ac470be0da..121faf1e11ad 100644
--- a/fs/xfs/libxfs/xfs_alloc.h
+++ b/fs/xfs/libxfs/xfs_alloc.h
@@ -232,7 +232,7 @@ xfs_buf_to_agfl_bno(

int __xfs_free_extent_later(struct xfs_trans *tp, xfs_fsblock_t bno,
xfs_filblks_t len, const struct xfs_owner_info *oinfo,
- bool skip_discard);
+ enum xfs_ag_resv_type type, bool skip_discard);

/*
* List of extents to be free "later".
@@ -245,6 +245,7 @@ struct xfs_extent_free_item {
xfs_extlen_t xefi_blockcount;/* number of blocks in extent */
struct xfs_perag *xefi_pag;
unsigned int xefi_flags;
+ enum xfs_ag_resv_type xefi_type;
};

void xfs_extent_free_get_group(struct xfs_mount *mp,
@@ -259,9 +260,10 @@ xfs_free_extent_later(
struct xfs_trans *tp,
xfs_fsblock_t bno,
xfs_filblks_t len,
- const struct xfs_owner_info *oinfo)
+ const struct xfs_owner_info *oinfo,
+ enum xfs_ag_resv_type type)
{
- return __xfs_free_extent_later(tp, bno, len, oinfo, false);
+ return __xfs_free_extent_later(tp, bno, len, oinfo, type, false);
}

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index fef35696adb7..30c931b38853 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -574,7 +574,8 @@ xfs_bmap_btree_to_extents(
return error;

xfs_rmap_ino_bmbt_owner(&oinfo, ip->i_ino, whichfork);
- error = xfs_free_extent_later(cur->bc_tp, cbno, 1, &oinfo);
+ error = xfs_free_extent_later(cur->bc_tp, cbno, 1, &oinfo,
+ XFS_AG_RESV_NONE);
if (error)
return error;

@@ -5236,8 +5237,9 @@ xfs_bmap_del_extent_real(
} else {
error = __xfs_free_extent_later(tp, del->br_startblock,
del->br_blockcount, NULL,
- (bflags & XFS_BMAPI_NODISCARD) ||
- del->br_state == XFS_EXT_UNWRITTEN);
+ XFS_AG_RESV_NONE,
+ ((bflags & XFS_BMAPI_NODISCARD) ||
+ del->br_state == XFS_EXT_UNWRITTEN));
if (error)
goto done;
}
diff --git a/fs/xfs/libxfs/xfs_bmap_btree.c b/fs/xfs/libxfs/xfs_bmap_btree.c
index 36564ae3084f..bf3f1b36fdd2 100644
--- a/fs/xfs/libxfs/xfs_bmap_btree.c
+++ b/fs/xfs/libxfs/xfs_bmap_btree.c
@@ -271,7 +271,8 @@ xfs_bmbt_free_block(
int error;

xfs_rmap_ino_bmbt_owner(&oinfo, ip->i_ino, cur->bc_ino.whichfork);
- error = xfs_free_extent_later(cur->bc_tp, fsbno, 1, &oinfo);
+ error = xfs_free_extent_later(cur->bc_tp, fsbno, 1, &oinfo,
+ XFS_AG_RESV_NONE);
if (error)
return error;

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index 34600f94c2f4..1e5fafbc0cdb 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -1853,8 +1853,8 @@ xfs_difree_inode_chunk(
/* not sparse, calculate extent info directly */
return xfs_free_extent_later(tp,
XFS_AGB_TO_FSB(mp, agno, sagbno),
- M_IGEO(mp)->ialloc_blks,
- &XFS_RMAP_OINFO_INODES);
+ M_IGEO(mp)->ialloc_blks, &XFS_RMAP_OINFO_INODES,
+ XFS_AG_RESV_NONE);
}

/* holemask is only 16-bits (fits in an unsigned long) */
@@ -1899,8 +1899,8 @@ xfs_difree_inode_chunk(
ASSERT(agbno % mp->m_sb.sb_spino_align == 0);
ASSERT(contigblk % mp->m_sb.sb_spino_align == 0);
error = xfs_free_extent_later(tp,
- XFS_AGB_TO_FSB(mp, agno, agbno),
- contigblk, &XFS_RMAP_OINFO_INODES);
+ XFS_AGB_TO_FSB(mp, agno, agbno), contigblk,
+ &XFS_RMAP_OINFO_INODES, XFS_AG_RESV_NONE);
if (error)
return error;

diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
index 5a945ae21b5d..9258f01c0015 100644
--- a/fs/xfs/libxfs/xfs_ialloc_btree.c
+++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
@@ -160,8 +160,7 @@ __xfs_inobt_free_block(

xfs_inobt_mod_blockcount(cur, -1);
fsbno = XFS_DADDR_TO_FSB(cur->bc_mp, xfs_buf_daddr(bp));
- return xfs_free_extent(cur->bc_tp, cur->bc_ag.pag,
- XFS_FSB_TO_AGBNO(cur->bc_mp, fsbno), 1,
+ return xfs_free_extent_later(cur->bc_tp, fsbno, 1,
&XFS_RMAP_OINFO_INOBT, resv);
}

diff --git a/fs/xfs/libxfs/xfs_refcount.c b/fs/xfs/libxfs/xfs_refcount.c
index b6e21433925c..70ab113c9cea 100644
--- a/fs/xfs/libxfs/xfs_refcount.c
+++ b/fs/xfs/libxfs/xfs_refcount.c
@@ -1152,7 +1152,8 @@ xfs_refcount_adjust_extents(
cur->bc_ag.pag->pag_agno,
tmp.rc_startblock);
error = xfs_free_extent_later(cur->bc_tp, fsbno,
- tmp.rc_blockcount, NULL);
+ tmp.rc_blockcount, NULL,
+ XFS_AG_RESV_NONE);
if (error)
goto out_error;
}
@@ -1213,7 +1214,8 @@ xfs_refcount_adjust_extents(
cur->bc_ag.pag->pag_agno,
ext.rc_startblock);
error = xfs_free_extent_later(cur->bc_tp, fsbno,
- ext.rc_blockcount, NULL);
+ ext.rc_blockcount, NULL,
+ XFS_AG_RESV_NONE);
if (error)
goto out_error;
}
@@ -1981,7 +1983,8 @@ xfs_refcount_recover_cow_leftovers(

/* Free the block. */
error = xfs_free_extent_later(tp, fsb,
- rr->rr_rrec.rc_blockcount, NULL);
+ rr->rr_rrec.rc_blockcount, NULL,
+ XFS_AG_RESV_NONE);
if (error)
goto out_trans;

diff --git a/fs/xfs/libxfs/xfs_refcount_btree.c b/fs/xfs/libxfs/xfs_refcount_btree.c
index d4afc5f4e6a5..5c3987d8dc24 100644
--- a/fs/xfs/libxfs/xfs_refcount_btree.c
+++ b/fs/xfs/libxfs/xfs_refcount_btree.c
@@ -106,19 +106,13 @@ xfs_refcountbt_free_block(
struct xfs_buf *agbp = cur->bc_ag.agbp;
struct xfs_agf *agf = agbp->b_addr;
xfs_fsblock_t fsbno = XFS_DADDR_TO_FSB(mp, xfs_buf_daddr(bp));
- int error;

trace_xfs_refcountbt_free_block(cur->bc_mp, cur->bc_ag.pag->pag_agno,
XFS_FSB_TO_AGBNO(cur->bc_mp, fsbno), 1);
be32_add_cpu(&agf->agf_refcount_blocks, -1);
xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_REFCOUNT_BLOCKS);
- error = xfs_free_extent(cur->bc_tp, cur->bc_ag.pag,
- XFS_FSB_TO_AGBNO(cur->bc_mp, fsbno), 1,
+ return xfs_free_extent_later(cur->bc_tp, fsbno, 1,
&XFS_RMAP_OINFO_REFC, XFS_AG_RESV_METADATA);
- if (error)
- return error;
-
- return error;
}

STATIC int
diff --git a/fs/xfs/xfs_extfree_item.c b/fs/xfs/xfs_extfree_item.c
index f9e36b810663..79e65bb6b0a2 100644
--- a/fs/xfs/xfs_extfree_item.c
+++ b/fs/xfs/xfs_extfree_item.c
@@ -365,7 +365,7 @@ xfs_trans_free_extent(
agbno, xefi->xefi_blockcount);

error = __xfs_free_extent(tp, xefi->xefi_pag, agbno,
- xefi->xefi_blockcount, &oinfo, XFS_AG_RESV_NONE,
+ xefi->xefi_blockcount, &oinfo, xefi->xefi_type,
xefi->xefi_flags & XFS_EFI_SKIP_DISCARD);

/*
@@ -644,6 +644,7 @@ xfs_efi_item_recover(
for (i = 0; i < efip->efi_format.efi_nextents; i++) {
struct xfs_extent_free_item fake = {
.xefi_owner = XFS_RMAP_OWN_UNKNOWN,
+ .xefi_type = XFS_AG_RESV_NONE,
};
struct xfs_extent *extp;

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index abcc559f3c64..eb9102453aff 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -617,7 +617,8 @@ xfs_reflink_cancel_cow_blocks(
del.br_blockcount);

error = xfs_free_extent_later(*tpp, del.br_startblock,
- del.br_blockcount, NULL);
+ del.br_blockcount, NULL,
+ XFS_AG_RESV_NONE);
if (error)
break;

--
2.40.1