4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Joe Thornber ejt@redhat.com
[ Upstream commit 3ab91828166895600efd9cdc3a0eb32001f7204a ]
Committing a transaction can consume some metadata of it's own, we now reserve a small amount of metadata to cover this. Free metadata reported by the kernel will not include this reserve.
If any of the reserve has been used after a commit we enter a new internal state PM_OUT_OF_METADATA_SPACE. This is reported as PM_READ_ONLY, so no userland changes are needed. If the metadata device is resized the pool will move back to PM_WRITE.
These changes mean we never need to abort and rollback a transaction due to running out of metadata space. This is particularly important because there have been a handful of reports of data corruption against DM thin-provisioning that can all be attributed to the thin-pool having ran out of metadata space.
Signed-off-by: Joe Thornber ejt@redhat.com Signed-off-by: Mike Snitzer snitzer@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/dm-thin-metadata.c | 36 ++++++++++++++++++++ drivers/md/dm-thin.c | 73 +++++++++++++++++++++++++++++++++++++----- 2 files changed, 100 insertions(+), 9 deletions(-)
--- a/drivers/md/dm-thin-metadata.c +++ b/drivers/md/dm-thin-metadata.c @@ -190,6 +190,12 @@ struct dm_pool_metadata { sector_t data_block_size;
/* + * We reserve a section of the metadata for commit overhead. + * All reported space does *not* include this. + */ + dm_block_t metadata_reserve; + + /* * Set if a transaction has to be aborted but the attempt to roll back * to the previous (good) transaction failed. The only pool metadata * operation possible in this state is the closing of the device. @@ -827,6 +833,22 @@ static int __commit_transaction(struct d return dm_tm_commit(pmd->tm, sblock); }
+static void __set_metadata_reserve(struct dm_pool_metadata *pmd) +{ + int r; + dm_block_t total; + dm_block_t max_blocks = 4096; /* 16M */ + + r = dm_sm_get_nr_blocks(pmd->metadata_sm, &total); + if (r) { + DMERR("could not get size of metadata device"); + pmd->metadata_reserve = max_blocks; + } else { + sector_div(total, 10); + pmd->metadata_reserve = min(max_blocks, total); + } +} + struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev, sector_t data_block_size, bool format_device) @@ -860,6 +882,8 @@ struct dm_pool_metadata *dm_pool_metadat return ERR_PTR(r); }
+ __set_metadata_reserve(pmd); + return pmd; }
@@ -1763,6 +1787,13 @@ int dm_pool_get_free_metadata_block_coun down_read(&pmd->root_lock); if (!pmd->fail_io) r = dm_sm_get_nr_free(pmd->metadata_sm, result); + + if (!r) { + if (*result < pmd->metadata_reserve) + *result = 0; + else + *result -= pmd->metadata_reserve; + } up_read(&pmd->root_lock);
return r; @@ -1875,8 +1906,11 @@ int dm_pool_resize_metadata_dev(struct d int r = -EINVAL;
down_write(&pmd->root_lock); - if (!pmd->fail_io) + if (!pmd->fail_io) { r = __resize_space_map(pmd->metadata_sm, new_count); + if (!r) + __set_metadata_reserve(pmd); + } up_write(&pmd->root_lock);
return r; --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -200,7 +200,13 @@ struct dm_thin_new_mapping; enum pool_mode { PM_WRITE, /* metadata may be changed */ PM_OUT_OF_DATA_SPACE, /* metadata may be changed, though data may not be allocated */ + + /* + * Like READ_ONLY, except may switch back to WRITE on metadata resize. Reported as READ_ONLY. + */ + PM_OUT_OF_METADATA_SPACE, PM_READ_ONLY, /* metadata may not be changed */ + PM_FAIL, /* all I/O fails */ };
@@ -1301,7 +1307,35 @@ static void set_pool_mode(struct pool *p
static void requeue_bios(struct pool *pool);
-static void check_for_space(struct pool *pool) +static bool is_read_only_pool_mode(enum pool_mode mode) +{ + return (mode == PM_OUT_OF_METADATA_SPACE || mode == PM_READ_ONLY); +} + +static bool is_read_only(struct pool *pool) +{ + return is_read_only_pool_mode(get_pool_mode(pool)); +} + +static void check_for_metadata_space(struct pool *pool) +{ + int r; + const char *ooms_reason = NULL; + dm_block_t nr_free; + + r = dm_pool_get_free_metadata_block_count(pool->pmd, &nr_free); + if (r) + ooms_reason = "Could not get free metadata blocks"; + else if (!nr_free) + ooms_reason = "No free metadata blocks"; + + if (ooms_reason && !is_read_only(pool)) { + DMERR("%s", ooms_reason); + set_pool_mode(pool, PM_OUT_OF_METADATA_SPACE); + } +} + +static void check_for_data_space(struct pool *pool) { int r; dm_block_t nr_free; @@ -1327,14 +1361,16 @@ static int commit(struct pool *pool) { int r;
- if (get_pool_mode(pool) >= PM_READ_ONLY) + if (get_pool_mode(pool) >= PM_OUT_OF_METADATA_SPACE) return -EINVAL;
r = dm_pool_commit_metadata(pool->pmd); if (r) metadata_operation_failed(pool, "dm_pool_commit_metadata", r); - else - check_for_space(pool); + else { + check_for_metadata_space(pool); + check_for_data_space(pool); + }
return r; } @@ -1400,6 +1436,19 @@ static int alloc_data_block(struct thin_ return r; }
+ r = dm_pool_get_free_metadata_block_count(pool->pmd, &free_blocks); + if (r) { + metadata_operation_failed(pool, "dm_pool_get_free_metadata_block_count", r); + return r; + } + + if (!free_blocks) { + /* Let's commit before we use up the metadata reserve. */ + r = commit(pool); + if (r) + return r; + } + return 0; }
@@ -1431,6 +1480,7 @@ static int should_error_unserviceable_bi case PM_OUT_OF_DATA_SPACE: return pool->pf.error_if_no_space ? -ENOSPC : 0;
+ case PM_OUT_OF_METADATA_SPACE: case PM_READ_ONLY: case PM_FAIL: return -EIO; @@ -2401,8 +2451,9 @@ static void set_pool_mode(struct pool *p error_retry_list(pool); break;
+ case PM_OUT_OF_METADATA_SPACE: case PM_READ_ONLY: - if (old_mode != new_mode) + if (!is_read_only_pool_mode(old_mode)) notify_of_pool_mode_change(pool, "read-only"); dm_pool_metadata_read_only(pool->pmd); pool->process_bio = process_bio_read_only; @@ -3333,6 +3384,10 @@ static int maybe_resize_metadata_dev(str DMINFO("%s: growing the metadata device from %llu to %llu blocks", dm_device_name(pool->pool_md), sb_metadata_dev_size, metadata_dev_size); + + if (get_pool_mode(pool) == PM_OUT_OF_METADATA_SPACE) + set_pool_mode(pool, PM_WRITE); + r = dm_pool_resize_metadata_dev(pool->pmd, metadata_dev_size); if (r) { metadata_operation_failed(pool, "dm_pool_resize_metadata_dev", r); @@ -3636,7 +3691,7 @@ static int pool_message(struct dm_target struct pool_c *pt = ti->private; struct pool *pool = pt->pool;
- if (get_pool_mode(pool) >= PM_READ_ONLY) { + if (get_pool_mode(pool) >= PM_OUT_OF_METADATA_SPACE) { DMERR("%s: unable to service pool target messages in READ_ONLY or FAIL mode", dm_device_name(pool->pool_md)); return -EOPNOTSUPP; @@ -3710,6 +3765,7 @@ static void pool_status(struct dm_target dm_block_t nr_blocks_data; dm_block_t nr_blocks_metadata; dm_block_t held_root; + enum pool_mode mode; char buf[BDEVNAME_SIZE]; char buf2[BDEVNAME_SIZE]; struct pool_c *pt = ti->private; @@ -3780,9 +3836,10 @@ static void pool_status(struct dm_target else DMEMIT("- ");
- if (pool->pf.mode == PM_OUT_OF_DATA_SPACE) + mode = get_pool_mode(pool); + if (mode == PM_OUT_OF_DATA_SPACE) DMEMIT("out_of_data_space "); - else if (pool->pf.mode == PM_READ_ONLY) + else if (is_read_only_pool_mode(mode)) DMEMIT("ro "); else DMEMIT("rw ");