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dm: fix deadlock when swapping to encrypted device
commit a666e5c05e
upstream.
The system would deadlock when swapping to a dm-crypt device. The reason
is that for each incoming write bio, dm-crypt allocates memory that holds
encrypted data. These excessive allocations exhaust all the memory and the
result is either deadlock or OOM trigger.
This patch limits the number of in-flight swap bios, so that the memory
consumed by dm-crypt is limited. The limit is enforced if the target set
the "limit_swap_bios" variable and if the bio has REQ_SWAP set.
Non-swap bios are not affected becuase taking the semaphore would cause
performance degradation.
This is similar to request-based drivers - they will also block when the
number of requests is over the limit.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
parent
fd3b7e07d3
commit
5233c47c8d
4 changed files with 70 additions and 0 deletions
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@ -106,6 +106,10 @@ struct mapped_device {
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struct block_device *bdev;
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int swap_bios;
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struct semaphore swap_bios_semaphore;
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struct mutex swap_bios_lock;
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struct dm_stats stats;
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/* for blk-mq request-based DM support */
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@ -2737,6 +2737,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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wake_up_process(cc->write_thread);
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ti->num_flush_bios = 1;
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ti->limit_swap_bios = true;
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return 0;
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@ -146,6 +146,16 @@ EXPORT_SYMBOL_GPL(dm_bio_get_target_bio_nr);
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#define DM_NUMA_NODE NUMA_NO_NODE
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static int dm_numa_node = DM_NUMA_NODE;
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#define DEFAULT_SWAP_BIOS (8 * 1048576 / PAGE_SIZE)
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static int swap_bios = DEFAULT_SWAP_BIOS;
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static int get_swap_bios(void)
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{
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int latch = READ_ONCE(swap_bios);
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if (unlikely(latch <= 0))
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latch = DEFAULT_SWAP_BIOS;
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return latch;
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}
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/*
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* For mempools pre-allocation at the table loading time.
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*/
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@ -972,6 +982,11 @@ void disable_write_zeroes(struct mapped_device *md)
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limits->max_write_zeroes_sectors = 0;
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}
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static bool swap_bios_limit(struct dm_target *ti, struct bio *bio)
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{
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return unlikely((bio->bi_opf & REQ_SWAP) != 0) && unlikely(ti->limit_swap_bios);
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}
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static void clone_endio(struct bio *bio)
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{
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blk_status_t error = bio->bi_status;
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@ -1009,6 +1024,11 @@ static void clone_endio(struct bio *bio)
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}
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}
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if (unlikely(swap_bios_limit(tio->ti, bio))) {
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struct mapped_device *md = io->md;
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up(&md->swap_bios_semaphore);
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}
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free_tio(tio);
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dec_pending(io, error);
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}
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@ -1263,6 +1283,22 @@ void dm_remap_zone_report(struct dm_target *ti, sector_t start,
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}
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EXPORT_SYMBOL_GPL(dm_remap_zone_report);
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static noinline void __set_swap_bios_limit(struct mapped_device *md, int latch)
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{
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mutex_lock(&md->swap_bios_lock);
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while (latch < md->swap_bios) {
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cond_resched();
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down(&md->swap_bios_semaphore);
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md->swap_bios--;
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}
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while (latch > md->swap_bios) {
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cond_resched();
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up(&md->swap_bios_semaphore);
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md->swap_bios++;
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}
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mutex_unlock(&md->swap_bios_lock);
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}
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static blk_qc_t __map_bio(struct dm_target_io *tio)
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{
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int r;
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@ -1283,6 +1319,14 @@ static blk_qc_t __map_bio(struct dm_target_io *tio)
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atomic_inc(&io->io_count);
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sector = clone->bi_iter.bi_sector;
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if (unlikely(swap_bios_limit(ti, clone))) {
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struct mapped_device *md = io->md;
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int latch = get_swap_bios();
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if (unlikely(latch != md->swap_bios))
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__set_swap_bios_limit(md, latch);
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down(&md->swap_bios_semaphore);
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}
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r = ti->type->map(ti, clone);
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switch (r) {
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case DM_MAPIO_SUBMITTED:
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@ -1297,10 +1341,18 @@ static blk_qc_t __map_bio(struct dm_target_io *tio)
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ret = generic_make_request(clone);
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break;
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case DM_MAPIO_KILL:
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if (unlikely(swap_bios_limit(ti, clone))) {
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struct mapped_device *md = io->md;
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up(&md->swap_bios_semaphore);
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}
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free_tio(tio);
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dec_pending(io, BLK_STS_IOERR);
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break;
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case DM_MAPIO_REQUEUE:
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if (unlikely(swap_bios_limit(ti, clone))) {
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struct mapped_device *md = io->md;
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up(&md->swap_bios_semaphore);
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}
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free_tio(tio);
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dec_pending(io, BLK_STS_DM_REQUEUE);
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break;
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@ -1894,6 +1946,7 @@ static void cleanup_mapped_device(struct mapped_device *md)
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mutex_destroy(&md->suspend_lock);
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mutex_destroy(&md->type_lock);
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mutex_destroy(&md->table_devices_lock);
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mutex_destroy(&md->swap_bios_lock);
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dm_mq_cleanup_mapped_device(md);
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}
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@ -1963,6 +2016,10 @@ static struct mapped_device *alloc_dev(int minor)
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init_waitqueue_head(&md->eventq);
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init_completion(&md->kobj_holder.completion);
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md->swap_bios = get_swap_bios();
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sema_init(&md->swap_bios_semaphore, md->swap_bios);
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mutex_init(&md->swap_bios_lock);
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md->disk->major = _major;
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md->disk->first_minor = minor;
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md->disk->fops = &dm_blk_dops;
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@ -3245,6 +3302,9 @@ MODULE_PARM_DESC(reserved_bio_based_ios, "Reserved IOs in bio-based mempools");
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module_param(dm_numa_node, int, S_IRUGO | S_IWUSR);
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MODULE_PARM_DESC(dm_numa_node, "NUMA node for DM device memory allocations");
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module_param(swap_bios, int, S_IRUGO | S_IWUSR);
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MODULE_PARM_DESC(swap_bios, "Maximum allowed inflight swap IOs");
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MODULE_DESCRIPTION(DM_NAME " driver");
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MODULE_AUTHOR("Joe Thornber <dm-devel@redhat.com>");
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MODULE_LICENSE("GPL");
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@ -316,6 +316,11 @@ struct dm_target {
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* whether or not its underlying devices have support.
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*/
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bool discards_supported:1;
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/*
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* Set if we need to limit the number of in-flight bios when swapping.
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*/
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bool limit_swap_bios:1;
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};
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/* Each target can link one of these into the table */
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