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ocfs2: cluster: use an on-stack bio for the heartbeat write

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The disk heartbeat write always covers this node's own single slot, i.e. 
one heartbeat block that lives within a single page.  It is submitted by
o2hb_issue_node_write() and waited on by the caller before the ctxt goes
out of scope, so its lifetime is well bounded.

Turn it into an on-stack bio embedded in struct o2hb_bio_wait_ctxt rather
than allocating one from the mempool.  This removes any allocation from
the fence-critical write path entirely: a delayed or blocked heartbeat
write is what leads to the local node being fenced, so it should not
depend on the state of a shared bio pool.

Because the bio is embedded rather than allocated, add a dedicated
o2hb_write_bio_end_io() that does not call bio_put(), and tear the bio
down with bio_uninit() once the caller has waited on the I/O.

The read path still allocates via o2hb_setup_one_bio() with GFP_NOFS,
since it issues a variable number of bios in a loop.

Link: https://lore.kernel.org/20260710071756.3586797-2-joseph.qi@linux.alibaba.com
Signed-off-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Joseph Qi
2026-07-10 15:17:56 +08:00
committed by Andrew Morton
parent 609d45af83
commit 041c9d0ab5
1 changed files with 45 additions and 5 deletions
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50
fs/ocfs2/cluster/heartbeat.c
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@@ -272,6 +272,9 @@ struct o2hb_bio_wait_ctxt {
atomic_t wc_num_reqs;
struct completion wc_io_complete;
int wc_error;
/* On-stack bio used by the synchronous write path only. */
struct bio wc_write_bio;
struct bio_vec wc_write_bvec;
};
#define O2HB_NEGO_TIMEOUT_MS (O2HB_MAX_WRITE_TIMEOUT_MS/2)
@@ -507,6 +510,23 @@ static void o2hb_bio_end_io(struct bio *bio)
bio_put(bio);
}
/*
* End I/O for the synchronous write path. The write bio is embedded in
* the wait ctxt rather than allocated, so it must not be freed here; it
* is torn down with bio_uninit() once the caller has waited on it.
*/
static void o2hb_write_bio_end_io(struct bio *bio)
{
struct o2hb_bio_wait_ctxt *wc = bio->bi_private;
if (bio->bi_status) {
mlog(ML_ERROR, "IO Error %d\n", bio->bi_status);
wc->wc_error = blk_status_to_errno(bio->bi_status);
}
o2hb_bio_wait_dec(wc, 1);
}
/* Setup a Bio to cover I/O against num_slots slots starting at
* start_slot. */
static struct bio *o2hb_setup_one_bio(struct o2hb_region *reg,
@@ -582,7 +602,11 @@ static int o2hb_issue_node_write(struct o2hb_region *reg,
struct o2hb_bio_wait_ctxt *write_wc)
{
unsigned int slot;
struct bio *bio;
unsigned int bits = reg->hr_block_bits;
unsigned int spp = reg->hr_slots_per_page;
unsigned int vec_start, vec_len;
struct page *page;
struct bio *bio = &write_wc->wc_write_bio;
o2hb_bio_wait_init(write_wc);
@@ -590,8 +614,21 @@ static int o2hb_issue_node_write(struct o2hb_region *reg,
if (slot >= O2NM_MAX_NODES)
return -EINVAL;
bio = o2hb_setup_one_bio(reg, write_wc, &slot, slot+1,
REQ_OP_WRITE | REQ_SYNC);
/*
* The heartbeat write always covers our own single slot, i.e. one
* block that lives within a single page. Use an on-stack bio (embedded
* in write_wc) so this fence-critical path never has to allocate.
*/
bio_init(bio, reg_bdev(reg), &write_wc->wc_write_bvec, 1,
REQ_OP_WRITE | REQ_SYNC);
bio->bi_iter.bi_sector = (reg->hr_start_block + slot) << (bits - 9);
bio->bi_private = write_wc;
bio->bi_end_io = o2hb_write_bio_end_io;
page = reg->hr_slot_data[slot / spp];
vec_start = (slot << bits) % PAGE_SIZE;
vec_len = PAGE_SIZE / spp;
__bio_add_page(bio, page, vec_len, vec_start);
atomic_inc(&write_wc->wc_num_reqs);
submit_bio(bio);
@@ -1133,6 +1170,7 @@ static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
* people we find in our steady state have seen us.
*/
o2hb_wait_on_io(&write_wc);
bio_uninit(&write_wc.wc_write_bio);
if (write_wc.wc_error) {
/* Do not re-arm the write timeout on I/O error - we
* can't be sure that the new block ever made it to
@@ -1245,10 +1283,12 @@ static int o2hb_thread(void *data)
if (!reg->hr_unclean_stop && !reg->hr_aborted_start) {
o2hb_prepare_block(reg, 0);
ret = o2hb_issue_node_write(reg, &write_wc);
if (ret == 0)
if (ret == 0) {
o2hb_wait_on_io(&write_wc);
else
bio_uninit(&write_wc.wc_write_bio);
} else {
mlog_errno(ret);
}
}
/* Unpin node */