From 9571f829f30a89b888ec4c3a72f5a04573f0e058 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Tue, 31 May 2022 12:16:49 -0400 Subject: [PATCH] dm table: fix dm_table_supports_poll to return false if no data devices It was reported that the "generic/250" test in xfstests (which uses the dm-error target) demonstrates a regression where the kernel crashes in bioset_exit(). Since commit cfc97abcbe0b ("dm: conditionally enable BIOSET_PERCPU_CACHE for dm_io bioset") the bioset_init() for the dm_io bioset will setup the bioset's per-cpu alloc cache if all devices have QUEUE_FLAG_POLL set. But there was an bug where a target that doesn't have any data devices (and that doesn't even set the .iterate_devices dm target callback) will incorrectly return true from dm_table_supports_poll(). Fix this by updating dm_table_supports_poll() to follow dm-table.c's well-worn pattern for testing that _all_ targets in a DM table do in fact have underlying devices that set QUEUE_FLAG_POLL. NOTE: An additional block fix is still needed so that bio_alloc_cache_destroy() clears the bioset's ->cache member. Otherwise, a DM device's table reload that transitions the DM device's bioset from using a per-cpu alloc cache to _not_ using one will result in bioset_exit() crashing in bio_alloc_cache_destroy() because dm's dm_io bioset ("io_bs") was left with a stale ->cache member. Fixes: cfc97abcbe0b ("dm: conditionally enable BIOSET_PERCPU_CACHE for dm_io bioset") Reported-by: Matthew Wilcox Reported-by: Dave Chinner Signed-off-by: Mike Snitzer --- drivers/md/dm-table.c | 19 +++++++++++++++---- 1 file changed, 15 insertions(+), 4 deletions(-) diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c index a37c7b763643..0e833a154b31 100644 --- a/drivers/md/dm-table.c +++ b/drivers/md/dm-table.c @@ -1005,7 +1005,7 @@ bool dm_table_request_based(struct dm_table *t) return __table_type_request_based(dm_table_get_type(t)); } -static int dm_table_supports_poll(struct dm_table *t); +static bool dm_table_supports_poll(struct dm_table *t); static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *md) { @@ -1027,7 +1027,7 @@ static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device * per_io_data_size = max(per_io_data_size, ti->per_io_data_size); min_pool_size = max(min_pool_size, ti->num_flush_bios); } - poll_supported = !!dm_table_supports_poll(t); + poll_supported = dm_table_supports_poll(t); } t->mempools = dm_alloc_md_mempools(md, type, per_io_data_size, min_pool_size, @@ -1547,9 +1547,20 @@ static int count_device(struct dm_target *ti, struct dm_dev *dev, return 0; } -static int dm_table_supports_poll(struct dm_table *t) +static bool dm_table_supports_poll(struct dm_table *t) { - return !dm_table_any_dev_attr(t, device_not_poll_capable, NULL); + struct dm_target *ti; + unsigned i = 0; + + while (i < dm_table_get_num_targets(t)) { + ti = dm_table_get_target(t, i++); + + if (!ti->type->iterate_devices || + ti->type->iterate_devices(ti, device_not_poll_capable, NULL)) + return false; + } + + return true; } /*