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authorJoe Thornber <ejt@redhat.com>2018-09-10 16:50:09 +0100
committerMike Snitzer <snitzer@redhat.com>2018-09-10 17:03:18 -0400
commit3ab91828166895600efd9cdc3a0eb32001f7204a (patch)
treeb0a357366b35d36d697c8f6f1d2f6fede0074b63 /drivers/md/dm-thin-metadata.c
parent5380c05b682991a6818c3755d450a3e87eeac0e5 (diff)
dm thin metadata: try to avoid ever aborting transactions
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>
Diffstat (limited to 'drivers/md/dm-thin-metadata.c')
-rw-r--r--drivers/md/dm-thin-metadata.c36
1 files changed, 35 insertions, 1 deletions
diff --git a/drivers/md/dm-thin-metadata.c b/drivers/md/dm-thin-metadata.c
index 72142021b5c9..74f6770c70b1 100644
--- a/drivers/md/dm-thin-metadata.c
+++ b/drivers/md/dm-thin-metadata.c
@@ -189,6 +189,12 @@ 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.
@@ -816,6 +822,22 @@ static int __commit_transaction(struct dm_pool_metadata *pmd)
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)
@@ -849,6 +871,8 @@ struct dm_pool_metadata *dm_pool_metadata_open(struct block_device *bdev,
return ERR_PTR(r);
}
+ __set_metadata_reserve(pmd);
+
return pmd;
}
@@ -1820,6 +1844,13 @@ int dm_pool_get_free_metadata_block_count(struct dm_pool_metadata *pmd,
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;
@@ -1932,8 +1963,11 @@ int dm_pool_resize_metadata_dev(struct dm_pool_metadata *pmd, dm_block_t new_cou
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;