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Pagecache bug handling #2

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c9232de
Try to handle potential Linux pagecache bug
YandexBuildBot Dec 24, 2015
e10f399
v0.23.11-pagecache
YandexBuildBot Dec 24, 2015
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6 changes: 6 additions & 0 deletions debian/changelog
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Original file line number Diff line number Diff line change
@@ -1,3 +1,9 @@
eblob (0.23.11-pagecache) unstable; urgency=medium

* Try to handle potential Linux pagecache bug

-- Anton Kortunov <toshik@yandex-team.ru> Thu, 24 Dec 2015 20:34:00 +0300

eblob (0.23.11) unstable; urgency=low

* iterate: verify checksum for entries while iterating a blob
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32 changes: 31 additions & 1 deletion library/blob.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1050,7 +1050,7 @@ static int eblob_mark_entry_removed(struct eblob_backend *b,
struct eblob_key *key, struct eblob_ram_control *old)
{
int err;
struct eblob_disk_control old_dc;
struct eblob_disk_control old_dc, blob_dc;
int64_t record_size = 0;

/* Add entry to list of removed entries */
Expand Down Expand Up @@ -1096,6 +1096,22 @@ static int eblob_mark_entry_removed(struct eblob_backend *b,
goto err;
}

/* Sanity: Check that blob on-disk header is not corrupted */
err = __eblob_read_ll(old->bctl->data_ctl.fd, &blob_dc, sizeof(blob_dc), old->data_offset);
if (err) {
EBLOB_WARNX(b->cfg.log, EBLOB_LOG_ERROR, "%s: __eblob_read_ll: FAILED: data, fd: %d, err: %d",
eblob_dump_id(key->id), old->bctl->index_ctl.fd, err);
goto err;
}

if (memcmp(&blob_dc.key, key, sizeof(key)) != 0) {
EBLOB_WARNX(b->cfg.log, EBLOB_LOG_ERROR, "keys mismatch: in-memory: %s, blob on-disk: %s",
eblob_dump_id_len(key->id, EBLOB_ID_SIZE),
eblob_dump_id_len(blob_dc.key.id, EBLOB_ID_SIZE));
err = -EINVAL;
goto err;
}

eblob_convert_disk_control(&old_dc);
/* size of the place occupied by the record in the index and the blob */
record_size = old_dc.disk_size + sizeof(struct eblob_disk_control);
Expand Down Expand Up @@ -1215,6 +1231,20 @@ static int eblob_commit_disk(struct eblob_backend *b, struct eblob_key *key,
goto err_out_exit;
}

/***************************************************************************
* ACHTUNG *
* Check for potential linux pagecache bug *
* Try to read few bites before header to fill page cache. *
***************************************************************************/
uint64_t tmp;
if (wc->ctl_data_offset > 8) {
err = __eblob_read_ll(wc->data_fd, &tmp, sizeof(tmp), wc->ctl_data_offset - 8);
if (err) {
eblob_dump_wc(b, key, wc, "eblob_commit_disk: ERROR sanity check failed", err);
goto err_out_exit;
}
}

err = __eblob_write_ll(wc->data_fd, &dc, sizeof(dc), wc->ctl_data_offset);
if (err) {
eblob_dump_wc(b, key, wc, "eblob_commit_disk: ERROR-write-data", err);
Expand Down