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btrfs: scrub: cleanup the remaining nodatasum fixup code
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Remove the remaining code that misused the page cache pages during
device replace and could cause data corruption for compressed nodatasum
extents. Such files do not normally exist but there's a bug that allows
this combination and the corruption was exposed by device replace fixup
code.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
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Qu Wenruo authored and David Sterba committed Aug 6, 2018
1 parent 46df06b commit 8b9b6f2
Showing 1 changed file with 0 additions and 289 deletions.
289 changes: 0 additions & 289 deletions fs/btrfs/scrub.c
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Original file line number Diff line number Diff line change
Expand Up @@ -188,15 +188,6 @@ struct scrub_ctx {
refcount_t refs;
};

struct scrub_fixup_nodatasum {
struct scrub_ctx *sctx;
struct btrfs_device *dev;
u64 logical;
struct btrfs_root *root;
struct btrfs_work work;
int mirror_num;
};

struct scrub_warning {
struct btrfs_path *path;
u64 extent_item_size;
Expand All @@ -215,8 +206,6 @@ struct full_stripe_lock {

static void scrub_pending_bio_inc(struct scrub_ctx *sctx);
static void scrub_pending_bio_dec(struct scrub_ctx *sctx);
static void scrub_pending_trans_workers_inc(struct scrub_ctx *sctx);
static void scrub_pending_trans_workers_dec(struct scrub_ctx *sctx);
static int scrub_handle_errored_block(struct scrub_block *sblock_to_check);
static int scrub_setup_recheck_block(struct scrub_block *original_sblock,
struct scrub_block *sblocks_for_recheck);
Expand Down Expand Up @@ -531,60 +520,6 @@ static int unlock_full_stripe(struct btrfs_fs_info *fs_info, u64 bytenr,
return ret;
}

/*
* used for workers that require transaction commits (i.e., for the
* NOCOW case)
*/
static void scrub_pending_trans_workers_inc(struct scrub_ctx *sctx)
{
struct btrfs_fs_info *fs_info = sctx->fs_info;

refcount_inc(&sctx->refs);
/*
* increment scrubs_running to prevent cancel requests from
* completing as long as a worker is running. we must also
* increment scrubs_paused to prevent deadlocking on pause
* requests used for transactions commits (as the worker uses a
* transaction context). it is safe to regard the worker
* as paused for all matters practical. effectively, we only
* avoid cancellation requests from completing.
*/
mutex_lock(&fs_info->scrub_lock);
atomic_inc(&fs_info->scrubs_running);
atomic_inc(&fs_info->scrubs_paused);
mutex_unlock(&fs_info->scrub_lock);

/*
* check if @scrubs_running=@scrubs_paused condition
* inside wait_event() is not an atomic operation.
* which means we may inc/dec @scrub_running/paused
* at any time. Let's wake up @scrub_pause_wait as
* much as we can to let commit transaction blocked less.
*/
wake_up(&fs_info->scrub_pause_wait);

atomic_inc(&sctx->workers_pending);
}

/* used for workers that require transaction commits */
static void scrub_pending_trans_workers_dec(struct scrub_ctx *sctx)
{
struct btrfs_fs_info *fs_info = sctx->fs_info;

/*
* see scrub_pending_trans_workers_inc() why we're pretending
* to be paused in the scrub counters
*/
mutex_lock(&fs_info->scrub_lock);
atomic_dec(&fs_info->scrubs_running);
atomic_dec(&fs_info->scrubs_paused);
mutex_unlock(&fs_info->scrub_lock);
atomic_dec(&sctx->workers_pending);
wake_up(&fs_info->scrub_pause_wait);
wake_up(&sctx->list_wait);
scrub_put_ctx(sctx);
}

static void scrub_free_csums(struct scrub_ctx *sctx)
{
while (!list_empty(&sctx->csum_list)) {
Expand Down Expand Up @@ -858,194 +793,6 @@ static void scrub_print_warning(const char *errstr, struct scrub_block *sblock)
btrfs_free_path(path);
}

static int scrub_fixup_readpage(u64 inum, u64 offset, u64 root, void *fixup_ctx)
{
struct page *page = NULL;
unsigned long index;
struct scrub_fixup_nodatasum *fixup = fixup_ctx;
int ret;
int corrected = 0;
struct btrfs_key key;
struct inode *inode = NULL;
struct btrfs_fs_info *fs_info;
u64 end = offset + PAGE_SIZE - 1;
struct btrfs_root *local_root;
int srcu_index;

key.objectid = root;
key.type = BTRFS_ROOT_ITEM_KEY;
key.offset = (u64)-1;

fs_info = fixup->root->fs_info;
srcu_index = srcu_read_lock(&fs_info->subvol_srcu);

local_root = btrfs_read_fs_root_no_name(fs_info, &key);
if (IS_ERR(local_root)) {
srcu_read_unlock(&fs_info->subvol_srcu, srcu_index);
return PTR_ERR(local_root);
}

key.type = BTRFS_INODE_ITEM_KEY;
key.objectid = inum;
key.offset = 0;
inode = btrfs_iget(fs_info->sb, &key, local_root, NULL);
srcu_read_unlock(&fs_info->subvol_srcu, srcu_index);
if (IS_ERR(inode))
return PTR_ERR(inode);

index = offset >> PAGE_SHIFT;

page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
if (!page) {
ret = -ENOMEM;
goto out;
}

if (PageUptodate(page)) {
if (PageDirty(page)) {
/*
* we need to write the data to the defect sector. the
* data that was in that sector is not in memory,
* because the page was modified. we must not write the
* modified page to that sector.
*
* TODO: what could be done here: wait for the delalloc
* runner to write out that page (might involve
* COW) and see whether the sector is still
* referenced afterwards.
*
* For the meantime, we'll treat this error
* incorrectable, although there is a chance that a
* later scrub will find the bad sector again and that
* there's no dirty page in memory, then.
*/
ret = -EIO;
goto out;
}
ret = repair_io_failure(fs_info, inum, offset, PAGE_SIZE,
fixup->logical, page,
offset - page_offset(page),
fixup->mirror_num);
unlock_page(page);
corrected = !ret;
} else {
/*
* we need to get good data first. the general readpage path
* will call repair_io_failure for us, we just have to make
* sure we read the bad mirror.
*/
ret = set_extent_bits(&BTRFS_I(inode)->io_tree, offset, end,
EXTENT_DAMAGED);
if (ret) {
/* set_extent_bits should give proper error */
WARN_ON(ret > 0);
if (ret > 0)
ret = -EFAULT;
goto out;
}

ret = extent_read_full_page(&BTRFS_I(inode)->io_tree, page,
btrfs_get_extent,
fixup->mirror_num);
wait_on_page_locked(page);

corrected = !test_range_bit(&BTRFS_I(inode)->io_tree, offset,
end, EXTENT_DAMAGED, 0, NULL);
if (!corrected)
clear_extent_bits(&BTRFS_I(inode)->io_tree, offset, end,
EXTENT_DAMAGED);
}

out:
if (page)
put_page(page);

iput(inode);

if (ret < 0)
return ret;

if (ret == 0 && corrected) {
/*
* we only need to call readpage for one of the inodes belonging
* to this extent. so make iterate_extent_inodes stop
*/
return 1;
}

return -EIO;
}

static void scrub_fixup_nodatasum(struct btrfs_work *work)
{
struct btrfs_fs_info *fs_info;
int ret;
struct scrub_fixup_nodatasum *fixup;
struct scrub_ctx *sctx;
struct btrfs_trans_handle *trans = NULL;
struct btrfs_path *path;
int uncorrectable = 0;

fixup = container_of(work, struct scrub_fixup_nodatasum, work);
sctx = fixup->sctx;
fs_info = fixup->root->fs_info;

path = btrfs_alloc_path();
if (!path) {
spin_lock(&sctx->stat_lock);
++sctx->stat.malloc_errors;
spin_unlock(&sctx->stat_lock);
uncorrectable = 1;
goto out;
}

trans = btrfs_join_transaction(fixup->root);
if (IS_ERR(trans)) {
uncorrectable = 1;
goto out;
}

/*
* the idea is to trigger a regular read through the standard path. we
* read a page from the (failed) logical address by specifying the
* corresponding copynum of the failed sector. thus, that readpage is
* expected to fail.
* that is the point where on-the-fly error correction will kick in
* (once it's finished) and rewrite the failed sector if a good copy
* can be found.
*/
ret = iterate_inodes_from_logical(fixup->logical, fs_info, path,
scrub_fixup_readpage, fixup, false);
if (ret < 0) {
uncorrectable = 1;
goto out;
}
WARN_ON(ret != 1);

spin_lock(&sctx->stat_lock);
++sctx->stat.corrected_errors;
spin_unlock(&sctx->stat_lock);

out:
if (trans && !IS_ERR(trans))
btrfs_end_transaction(trans);
if (uncorrectable) {
spin_lock(&sctx->stat_lock);
++sctx->stat.uncorrectable_errors;
spin_unlock(&sctx->stat_lock);
btrfs_dev_replace_stats_inc(
&fs_info->dev_replace.num_uncorrectable_read_errors);
btrfs_err_rl_in_rcu(fs_info,
"unable to fixup (nodatasum) error at logical %llu on dev %s",
fixup->logical, rcu_str_deref(fixup->dev->name));
}

btrfs_free_path(path);
kfree(fixup);

scrub_pending_trans_workers_dec(sctx);
}

static inline void scrub_get_recover(struct scrub_recover *recover)
{
refcount_inc(&recover->refs);
Expand Down Expand Up @@ -1239,42 +986,6 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
goto out;
}

/*
* NOTE: Even for nodatasum case, it's still possible that it's a
* compressed data extent, thus scrub_fixup_nodatasum(), which write
* inode page cache onto disk, could cause serious data corruption.
*
* So here we could only read from disk, and hope our recovery could
* reach disk before the newer write.
*/
if (0 && !is_metadata && !have_csum) {
struct scrub_fixup_nodatasum *fixup_nodatasum;

WARN_ON(sctx->is_dev_replace);

/*
* !is_metadata and !have_csum, this means that the data
* might not be COWed, that it might be modified
* concurrently. The general strategy to work on the
* commit root does not help in the case when COW is not
* used.
*/
fixup_nodatasum = kzalloc(sizeof(*fixup_nodatasum), GFP_NOFS);
if (!fixup_nodatasum)
goto did_not_correct_error;
fixup_nodatasum->sctx = sctx;
fixup_nodatasum->dev = dev;
fixup_nodatasum->logical = logical;
fixup_nodatasum->root = fs_info->extent_root;
fixup_nodatasum->mirror_num = failed_mirror_index + 1;
scrub_pending_trans_workers_inc(sctx);
btrfs_init_work(&fixup_nodatasum->work, btrfs_scrub_helper,
scrub_fixup_nodatasum, NULL, NULL);
btrfs_queue_work(fs_info->scrub_workers,
&fixup_nodatasum->work);
goto out;
}

/*
* now build and submit the bios for the other mirrors, check
* checksums.
Expand Down

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