From c5a415627be4758ebdd274de7148706d6713c7ec Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Mon, 14 Nov 2022 08:26:33 +0800
Subject: [PATCH] btrfs: raid56: prepare data checksums for later RMW
verification
This is for later data checksum verification at RMW time.
This patch will try to allocate the needed memory for a locked rbio if
the rbio is for data exclusively (we don't want to handle mixed bg yet).
The memory will be released when the rbio is finished.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/raid56.c | 74 +++++++++++++++++++++++++++++++++++++++++++++++
fs/btrfs/raid56.h | 12 ++++++++
2 files changed, 86 insertions(+)
diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 11be5d0a7eabe..5ef4fbb49df24 100644
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -20,6 +20,7 @@
#include "volumes.h"
#include "raid56.h"
#include "async-thread.h"
+#include "file-item.h"
/* set when additional merges to this rbio are not allowed */
#define RBIO_RMW_LOCKED_BIT 1
@@ -835,6 +836,11 @@ static void rbio_orig_end_io(struct btrfs_raid_bio *rbio, blk_status_t err)
struct bio *cur = bio_list_get(&rbio->bio_list);
struct bio *extra;
+ kfree(rbio->csum_buf);
+ bitmap_free(rbio->csum_bitmap);
+ rbio->csum_buf = NULL;
+ rbio->csum_bitmap = NULL;
+
/*
* Clear the data bitmap, as the rbio may be cached for later usage.
* do this before before unlock_stripe() so there will be no new bio
@@ -2048,6 +2054,67 @@ void raid56_parity_recover(struct bio *bio, struct btrfs_io_context *bioc,
start_async_work(rbio, recover_rbio_work);
}
+static void fill_data_csums(struct btrfs_raid_bio *rbio)
+{
+ struct btrfs_fs_info *fs_info = rbio->bioc->fs_info;
+ struct btrfs_root *csum_root = btrfs_csum_root(fs_info,
+ rbio->bioc->raid_map[0]);
+ const u64 start = rbio->bioc->raid_map[0];
+ const u32 len = (rbio->nr_data * rbio->stripe_nsectors) <<
+ fs_info->sectorsize_bits;
+ int ret;
+
+ /* The rbio should not have its csum buffer initialized. */
+ ASSERT(!rbio->csum_buf && !rbio->csum_bitmap);
+
+ /*
+ * Skip the csum search if:
+ *
+ * - The rbio doesn't belong to data block groups
+ * Then we are doing IO for tree blocks, no need to search csums.
+ *
+ * - The rbio belongs to mixed block groups
+ * This is to avoid deadlock, as we're already holding the full
+ * stripe lock, if we trigger a metadata read, and it needs to do
+ * raid56 recovery, we will deadlock.
+ */
+ if (!(rbio->bioc->map_type & BTRFS_BLOCK_GROUP_DATA) ||
+ rbio->bioc->map_type & BTRFS_BLOCK_GROUP_METADATA)
+ return;
+
+ rbio->csum_buf = kzalloc(rbio->nr_data * rbio->stripe_nsectors *
+ fs_info->csum_size, GFP_NOFS);
+ rbio->csum_bitmap = bitmap_zalloc(rbio->nr_data * rbio->stripe_nsectors,
+ GFP_NOFS);
+ if (!rbio->csum_buf || !rbio->csum_bitmap) {
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ ret = btrfs_lookup_csums_bitmap(csum_root, start, start + len - 1,
+ rbio->csum_buf, rbio->csum_bitmap);
+ if (ret < 0)
+ goto error;
+ if (bitmap_empty(rbio->csum_bitmap, len >> fs_info->sectorsize_bits))
+ goto no_csum;
+ return;
+
+error:
+ /*
+ * We failed to allocate memory or grab the csum, but it's not fatal,
+ * we can still continue. But better to warn users that RMW is no
+ * longer safe for this particular sub-stripe write.
+ */
+ btrfs_warn_rl(fs_info,
+"sub-stripe write for full stripe %llu is not safe, failed to get csum: %d",
+ rbio->bioc->raid_map[0], ret);
+no_csum:
+ kfree(rbio->csum_buf);
+ bitmap_free(rbio->csum_bitmap);
+ rbio->csum_buf = NULL;
+ rbio->csum_bitmap = NULL;
+}
+
static int rmw_read_and_wait(struct btrfs_raid_bio *rbio)
{
struct bio_list bio_list;
@@ -2056,6 +2123,13 @@ static int rmw_read_and_wait(struct btrfs_raid_bio *rbio)
bio_list_init(&bio_list);
+ /*
+ * Fill the data csums we need for data verification. We need to fill
+ * the csum_bitmap/csum_buf first, as our endio function will try to
+ * verify the data sectors.
+ */
+ fill_data_csums(rbio);
+
ret = rmw_assemble_read_bios(rbio, &bio_list);
if (ret < 0)
goto out;
diff --git a/fs/btrfs/raid56.h b/fs/btrfs/raid56.h
index a2e653e93fd8f..7c73a443939e6 100644
--- a/fs/btrfs/raid56.h
+++ b/fs/btrfs/raid56.h
@@ -129,6 +129,18 @@ struct btrfs_raid_bio {
* Thus making it much harder to iterate.
*/
unsigned long *error_bitmap;
+
+ /*
+ * Checksum buffer if the rbio is for data. The buffer should cover
+ * all data sectors (exlcuding P/Q sectors).
+ */
+ u8 *csum_buf;
+
+ /*
+ * Each bit represents if the corresponding sector has data csum found.
+ * Should only cover data sectors (excluding P/Q sectors).
+ */
+ unsigned long *csum_bitmap;
};
/*