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Btrfs: fix device replace of a missing RAID 5/6 device 

The original implementation of device replace on RAID 5/6 seems to have
missed support for replacing a missing device. When this is attempted,
we end up calling bio_add_page() on a bio with a NULL ->bi_bdev, which
crashes when we try to dereference it. This happens because
btrfs_map_block() has no choice but to return us the missing device
because RAID 5/6 don't have any alternate mirrors to read from, and a
missing device has a NULL bdev.

The idea implemented here is to handle the missing device case
separately, which better only happen when we're replacing a missing RAID
5/6 device. We use the new BTRFS_RBIO_REBUILD_MISSING operation to
reconstruct the data from parity, check it with
scrub_recheck_block_checksum(), and write it out with
scrub_write_block_to_dev_replace().

Reported-by: Philip <bugzilla@philip-seeger.de>
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=96141
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Chris Mason <clm@fb.com>
This commit is contained in:
Omar Sandoval 2015-06-19 11:52:51 -07:00 committed by Chris Mason
parent b4ee178268
commit 73ff61dbe5
1 changed files with 147 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

157
fs/btrfs/scrub.c
View File

@ -125,6 +125,7 @@ struct scrub_block {
/* It is for the data with checksum */
unsigned int data_corrected:1;
};
struct btrfs_work work;
};
/* Used for the chunks with parity stripe such RAID5/6 */
@ -2173,6 +2174,134 @@ again:
return 0;
}
static void scrub_missing_raid56_end_io(struct bio *bio, int error)
{
struct scrub_block *sblock = bio->bi_private;
struct btrfs_fs_info *fs_info = sblock->sctx->dev_root->fs_info;
if (error)
sblock->no_io_error_seen = 0;
btrfs_queue_work(fs_info->scrub_workers, &sblock->work);
}
static void scrub_missing_raid56_worker(struct btrfs_work *work)
{
struct scrub_block *sblock = container_of(work, struct scrub_block, work);
struct scrub_ctx *sctx = sblock->sctx;
struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
unsigned int is_metadata;
unsigned int have_csum;
u8 *csum;
u64 generation;
u64 logical;
struct btrfs_device *dev;
is_metadata = !(sblock->pagev[0]->flags & BTRFS_EXTENT_FLAG_DATA);
have_csum = sblock->pagev[0]->have_csum;
csum = sblock->pagev[0]->csum;
generation = sblock->pagev[0]->generation;
logical = sblock->pagev[0]->logical;
dev = sblock->pagev[0]->dev;
if (sblock->no_io_error_seen) {
scrub_recheck_block_checksum(fs_info, sblock, is_metadata,
have_csum, csum, generation,
sctx->csum_size);
}
if (!sblock->no_io_error_seen) {
spin_lock(&sctx->stat_lock);
sctx->stat.read_errors++;
spin_unlock(&sctx->stat_lock);
printk_ratelimited_in_rcu(KERN_ERR
"BTRFS: I/O error rebulding logical %llu for dev %s\n",
logical, rcu_str_deref(dev->name));
} else if (sblock->header_error || sblock->checksum_error) {
spin_lock(&sctx->stat_lock);
sctx->stat.uncorrectable_errors++;
spin_unlock(&sctx->stat_lock);
printk_ratelimited_in_rcu(KERN_ERR
"BTRFS: failed to rebuild valid logical %llu for dev %s\n",
logical, rcu_str_deref(dev->name));
} else {
scrub_write_block_to_dev_replace(sblock);
}
scrub_block_put(sblock);
if (sctx->is_dev_replace &&
atomic_read(&sctx->wr_ctx.flush_all_writes)) {
mutex_lock(&sctx->wr_ctx.wr_lock);
scrub_wr_submit(sctx);
mutex_unlock(&sctx->wr_ctx.wr_lock);
}
scrub_pending_bio_dec(sctx);
}
static void scrub_missing_raid56_pages(struct scrub_block *sblock)
{
struct scrub_ctx *sctx = sblock->sctx;
struct btrfs_fs_info *fs_info = sctx->dev_root->fs_info;
u64 length = sblock->page_count * PAGE_SIZE;
u64 logical = sblock->pagev[0]->logical;
struct btrfs_bio *bbio;
struct bio *bio;
struct btrfs_raid_bio *rbio;
int ret;
int i;
ret = btrfs_map_sblock(fs_info, REQ_GET_READ_MIRRORS, logical, &length,
&bbio, 0, 1);
if (ret || !bbio || !bbio->raid_map)
goto bbio_out;
if (WARN_ON(!sctx->is_dev_replace ||
!(bbio->map_type & BTRFS_BLOCK_GROUP_RAID56_MASK))) {
/*
* We shouldn't be scrubbing a missing device. Even for dev
* replace, we should only get here for RAID 5/6. We either
* managed to mount something with no mirrors remaining or
* there's a bug in scrub_remap_extent()/btrfs_map_block().
*/
goto bbio_out;
}
bio = btrfs_io_bio_alloc(GFP_NOFS, 0);
if (!bio)
goto bbio_out;
bio->bi_iter.bi_sector = logical >> 9;
bio->bi_private = sblock;
bio->bi_end_io = scrub_missing_raid56_end_io;
rbio = raid56_alloc_missing_rbio(sctx->dev_root, bio, bbio, length);
if (!rbio)
goto rbio_out;
for (i = 0; i < sblock->page_count; i++) {
struct scrub_page *spage = sblock->pagev[i];
raid56_add_scrub_pages(rbio, spage->page, spage->logical);
}
btrfs_init_work(&sblock->work, btrfs_scrub_helper,
scrub_missing_raid56_worker, NULL, NULL);
scrub_block_get(sblock);
scrub_pending_bio_inc(sctx);
raid56_submit_missing_rbio(rbio);
return;
rbio_out:
bio_put(bio);
bbio_out:
btrfs_put_bbio(bbio);
spin_lock(&sctx->stat_lock);
sctx->stat.malloc_errors++;
spin_unlock(&sctx->stat_lock);
}
static int scrub_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
u64 physical, struct btrfs_device *dev, u64 flags,
u64 gen, int mirror_num, u8 *csum, int force,
@ -2236,19 +2365,27 @@ leave_nomem:
}
WARN_ON(sblock->page_count == 0);
for (index = 0; index < sblock->page_count; index++) {
struct scrub_page *spage = sblock->pagev[index];
int ret;
if (dev->missing) {
/*
* This case should only be hit for RAID 5/6 device replace. See
* the comment in scrub_missing_raid56_pages() for details.
*/
scrub_missing_raid56_pages(sblock);
} else {
for (index = 0; index < sblock->page_count; index++) {
struct scrub_page *spage = sblock->pagev[index];
int ret;
ret = scrub_add_page_to_rd_bio(sctx, spage);
if (ret) {
scrub_block_put(sblock);
return ret;
ret = scrub_add_page_to_rd_bio(sctx, spage);
if (ret) {
scrub_block_put(sblock);
return ret;
}
}
}
if (force)
scrub_submit(sctx);
if (force)
scrub_submit(sctx);
}
/* last one frees, either here or in bio completion for last page */
scrub_block_put(sblock);