bcachefs: Fix nonce inconsistency in bch2_write_prep_encoded_data()

If we're moving an extent that was partially overwritten,
bch2_write_rechecksum() will trim it to the currenty live range.

If we then also want to compress it, it'll be decrypted - but the nonce
has been advanced for the overwritten start of the extent that we
dropped, and we were using the nonce we calculated before rechecksum().

Reported-by: Gabriel de Perthuis <g2p.code@gmail.com>
Fixes: 127d90d2823e ("bcachefs: bch2_write_prep_encoded_data() now returns errcode")
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/io_write.c b/fs/bcachefs/io_write.c
index 29671075e3f1d95b8617cdc964e18741fbaf8060..14c5c5c98d51d05e043069589d6d04901a2f2339 100644 (file)
--- a/fs/bcachefs/io_write.c
+++ b/fs/bcachefs/io_write.c
@@ -839,7 +839,6 @@ static noinline int bch2_write_prep_encoded_data(struct bch_write_op *op, struct
 {
        struct bch_fs *c = op->c;
        struct bio *bio = &op->wbio.bio;
-       struct nonce nonce = extent_nonce(op->version, op->crc);
        int ret = 0;
 
        BUG_ON(bio_sectors(bio) != op->crc.compressed_size);
@@ -866,6 +865,7 @@ static noinline int bch2_write_prep_encoded_data(struct bch_write_op *op, struct
         */
        if (crc_is_compressed(op->crc)) {
                /* Last point we can still verify checksum: */
+               struct nonce nonce = extent_nonce(op->version, op->crc);
                struct bch_csum csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, bio);
                if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
                        goto csum_err;
@@ -905,6 +905,7 @@ static noinline int bch2_write_prep_encoded_data(struct bch_write_op *op, struct
         */
        if (bch2_csum_type_is_encryption(op->crc.csum_type) &&
            (op->compression_opt || op->crc.csum_type != op->csum_type)) {
+               struct nonce nonce = extent_nonce(op->version, op->crc);
                struct bch_csum csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, bio);
                if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
                        goto csum_err;