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StaticHeader::setup Improve error reporting
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@GuillaumeGomez
GuillaumeGomez committed Jun 20, 2019
1 parent 5c6cf4c commit db984b7
Showing 1 changed file with 76 additions and 27 deletions.
103 changes: 76 additions & 27 deletions src/engine/strat_engine/backstore/metadata/bda.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -152,7 +152,11 @@ impl BDA {
F: Read + Seek + SyncAll,
{
let header = match StaticHeader::setup(f)? {
Some(header) => header,
Some(SetupResult::Ok(header)) => header,
Some(SetupResult::OkWithError(header, err)) => {
setup_warn(&header, err);
header
}
None => return Ok(None),
};

Expand Down Expand Up @@ -238,6 +242,37 @@ impl BDA {
}
}

fn setup_warn(header: &StaticHeader, err: StratisError) {
warn!("Experienced an I/O error while attempting to repair an ill-formed, \
unreadable, or stale signature block: {:?}.\n\
Returning device \"{:?}\" from pool \"{:?}\".",
err,
header.dev_uuid,
header.pool_uuid);
}

fn bda_write_check<F>(
f: &mut F,
bda_buf: &[u8],
which: MetadataLocation,
header: StaticHeader,
) -> StratisResult<Option<SetupResult>>
where
F: Read + Seek + SyncAll,
{
Ok(match BDA::write(f, &bda_buf, which) {
Ok(_) => Some(SetupResult::Ok(header)),
Err(err) => Some(SetupResult::OkWithError(header, StratisError::Io(err))),
})
}

#[derive(Debug)]
#[must_use]
pub enum SetupResult {
Ok(StaticHeader),
OkWithError(StaticHeader, StratisError),
}

#[derive(Eq, PartialEq)]
pub struct StaticHeader {
blkdev_size: Sectors,
Expand Down Expand Up @@ -270,17 +305,23 @@ impl StaticHeader {
}

/// Try to find a valid StaticHeader on a device.
///
/// Return the latest copy that validates as a Stratis BDA, however verify both
/// copies and if one validates but one does not, re-write the one that is incorrect. If both
/// copies are valid, but one is newer than the other, rewrite the older one to match.
///
/// Return None if it's not a Stratis device.
///
/// Return an error if the metadata seems to indicate that the device is
/// a Stratis device, but no well-formed signature block could be read.
///
/// Return an error if neither sigblock location can be read.
///
/// Return an error if the sigblocks differ in some unaccountable way.
/// Returns an error if a write intended to repair an ill-formed,
/// unreadable, or stale signature block failed.
fn setup<F>(f: &mut F) -> StratisResult<Option<StaticHeader>>
///
/// Return the latest copy alongside the associated error if a write intended to repair
/// an ill-formed, unreadable, or stale signature failed.
fn setup<F>(f: &mut F) -> StratisResult<Option<SetupResult>>
where
F: Read + Seek + SyncAll,
{
Expand All @@ -295,41 +336,36 @@ impl StaticHeader {
match (loc_1, loc_2) {
(Some(loc_1), Some(loc_2)) => {
if loc_1 == loc_2 {
Ok(Some(loc_1))
Ok(Some(SetupResult::Ok(loc_1)))
} else if loc_1.initialization_time == loc_2.initialization_time {
// Inexplicable disagreement among static headers
let err_str = "Appeared to be a Stratis device, but signature blocks disagree.";
Err(StratisError::Engine(ErrorEnum::Invalid, err_str.into()))
} else if loc_1.initialization_time > loc_2.initialization_time {
// If the first header block is newer, overwrite second with
// contents of first.
BDA::write(f, &buf_loc_1, MetadataLocation::Second)?;
Ok(Some(loc_1))
bda_write_check(f, &buf_loc_1, MetadataLocation::Second, loc_1)
} else {
// The second header block must be newer, so overwrite first
// with contents of second.
BDA::write(f, &buf_loc_2, MetadataLocation::First)?;
Ok(Some(loc_2))
bda_write_check(f, &buf_loc_2, MetadataLocation::First, loc_2)
}
}
(None, None) => Ok(None),
(Some(loc_1), None) => {
// Copy 1 has valid Stratis BDA, copy 2 has no magic, re-write copy 2
BDA::write(f, &buf_loc_1, MetadataLocation::Second)?;
Ok(Some(loc_1))
bda_write_check(f, &buf_loc_1, MetadataLocation::Second, loc_1)
}
(None, Some(loc_2)) => {
// Copy 2 has valid Stratis BDA, copy 1 has no magic, re-write copy 1
BDA::write(f, &buf_loc_2, MetadataLocation::First)?;
Ok(Some(loc_2))
bda_write_check(f, &buf_loc_2, MetadataLocation::First, loc_2)
}
}
}
(Ok(loc_1), Err(loc_2)) => {
// Re-write copy 2
if loc_1.is_some() {
BDA::write(f, &buf_loc_1, MetadataLocation::Second)?;
Ok(loc_1)
if let Some(loc_1) = loc_1 {
bda_write_check(f, &buf_loc_1, MetadataLocation::Second, loc_1)
} else {
// Location 1 doesn't have a signature, but location 2 did, but it got an error,
// lets return the error instead as this appears to be a stratis device that
Expand All @@ -339,9 +375,8 @@ impl StaticHeader {
}
(Err(loc_1), Ok(loc_2)) => {
// Re-write copy 1
if loc_2.is_some() {
BDA::write(f, &buf_loc_2, MetadataLocation::First)?;
Ok(loc_2)
if let Some(loc_2) = loc_2 {
bda_write_check(f, &buf_loc_2, MetadataLocation::First, loc_2)
} else {
// Location 2 doesn't have a signature, but location 1 did, but it got an error,
// lets return the error instead as this appears to be a stratis device that
Expand All @@ -360,10 +395,11 @@ impl StaticHeader {
// Copy 1 read OK, 2 resulted in an IO error
match StaticHeader::sigblock_from_buf(&buf_loc_1) {
Ok(loc_1) => {
if loc_1.is_some() {
BDA::write(f, &buf_loc_1, MetadataLocation::Second)?;
if let Some(loc_1) = loc_1 {
bda_write_check(f, &buf_loc_1, MetadataLocation::Second, loc_1)
} else {
Ok(None)
}
Ok(loc_1)
}
Err(e) => {
// Unable to determine if location 2 has a signature, but location 1 did,
Expand All @@ -377,10 +413,11 @@ impl StaticHeader {
// Copy 2 read OK, 1 resulted in IO Error
match StaticHeader::sigblock_from_buf(&buf_loc_2) {
Ok(loc_2) => {
if loc_2.is_some() {
BDA::write(f, &buf_loc_2, MetadataLocation::First)?;
}
Ok(loc_2)
Ok(if let Some(loc_2) = loc_2 {
bda_write_check(f, &buf_loc_2, MetadataLocation::First, loc_2)
} else {
None
})
}
Err(e) => {
// Unable to determine if location 1 has a signature, but location 2 did,
Expand All @@ -403,7 +440,19 @@ impl StaticHeader {
where
F: Read + Seek + SyncAll,
{
StaticHeader::setup(f).map(|sh| sh.map(|sh| (sh.pool_uuid, sh.dev_uuid)))
// Using setup() as a test of ownership sets a high bar. It is
// not sufficient to have STRAT_MAGIC to be considered "Ours",
// it must also have correct CRC, no weird stuff in fields,
// etc!
match StaticHeader::setup(f) {
Ok(Some(SetupResult::Ok(sh))) => Ok(Some((sh.pool_uuid, sh.dev_uuid))),
Ok(Some(SetupResult::OkWithError(sh, err))) => {
setup_warn(&sh, err);
Ok(Some((sh.pool_uuid, sh.dev_uuid)))
}
Ok(None) => Ok(None),
Err(err) => Err(err),
}
}

/// Generate a buf suitable for writing to blockdev
Expand Down

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