[pbs-devel] [PATCH v4 proxmox-backup 1/2] backup: check verify state of previous backup before allowing reuse

[pbs-devel] [PATCH v4 proxmox-backup 1/2] backup: check verify state of previous backup before allowing reuse

[Stefan Reiter]

Do not allow clients to reuse chunks from the previous backup if it has
a failed validation result. This would result in a new "successful"
backup that potentially references broken chunks.

If the previous backup has not been verified, assume it is fine and
continue on.

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---

v4:
* check earlier in upgrade_to_backup_protocol
* update error messages to include "valid"

 src/api2/backup.rs | 29 ++++++++++++++++++++++++++---
 1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/api2/backup.rs b/src/api2/backup.rs
index 9420b146..2b855554 100644
--- a/src/api2/backup.rs
+++ b/src/api2/backup.rs
@@ -113,7 +113,30 @@ async move {
         bail!("backup owner check failed ({} != {})", userid, owner);
     }
 
-    let last_backup = BackupInfo::last_backup(&datastore.base_path(), &backup_group, true).unwrap_or(None);
+    let last_backup = {
+        let info = BackupInfo::last_backup(&datastore.base_path(), &backup_group, true).unwrap_or(None);
+        if let Some(info) = info {
+            let (manifest, _) = datastore.load_manifest(&info.backup_dir)?;
+            let verify = manifest.unprotected["verify_state"].clone();
+            match serde_json::from_value::<SnapshotVerifyState>(verify) {
+                Ok(verify) => {
+                    if verify.state != "ok" {
+                        // verify failed, treat as if no previous backup exists
+                        None
+                    } else {
+                        Some(info)
+                    }
+                },
+                Err(_) => {
+                    // no verify state found, treat as valid
+                    Some(info)
+                }
+            }
+        } else {
+            None
+        }
+    };
+
     let backup_dir = BackupDir::new_with_group(backup_group.clone(), backup_time)?;
 
     let _last_guard = if let Some(last) = &last_backup {
@@ -355,7 +378,7 @@ fn create_fixed_index(
         let last_backup = match &env.last_backup {
             Some(info) => info,
             None => {
-                bail!("cannot reuse index - no previous backup exists");
+                bail!("cannot reuse index - no valid previous backup exists");
             }
         };
 
@@ -670,7 +693,7 @@ fn download_previous(
 
         let last_backup = match &env.last_backup {
             Some(info) => info,
-            None => bail!("no previous backup"),
+            None => bail!("no valid previous backup"),
         };
 
         let mut path = env.datastore.snapshot_path(&last_backup.backup_dir);
-- 
2.20.1

[pbs-devel] [PATCH v4 proxmox-backup 2/2] backup: check all referenced chunks actually exist

[Stefan Reiter]

A client can omit uploading chunks in the "known_chunks" list, those
then also won't be written on the server side. Check all those chunks
mentioned in the index but not uploaded for existance and report an
error if they don't exist instead of marking a potentially broken backup
as "successful".

This is only important if the base snapshot references corrupted chunks,
but has not been negatively verified. Also, it is important to only
verify this at the end, *after* all index writers are closed, since only
then can it be guaranteed that no GC will sweep referenced chunks away.

If a chunk is found missing, also mark the previous backup with a
verification failure, since we know the missing chunk has to referenced
in it (only way it could have been inserted to known_chunks with
checked=false). This has the benefit of automatically doing a
full-upload backup if the user attempts to retry after seeing the new
error, instead of requiring a manual verify or forget.

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
---

v4:
* no change

 src/api2/backup/environment.rs | 58 ++++++++++++++++++++++++++++++----
 1 file changed, 52 insertions(+), 6 deletions(-)

diff --git a/src/api2/backup/environment.rs b/src/api2/backup/environment.rs
index f635c6f7..22b96c22 100644
--- a/src/api2/backup/environment.rs
+++ b/src/api2/backup/environment.rs
@@ -9,7 +9,7 @@ use proxmox::tools::digest_to_hex;
 use proxmox::tools::fs::{replace_file, CreateOptions};
 use proxmox::api::{RpcEnvironment, RpcEnvironmentType};
 
-use crate::api2::types::Userid;
+use crate::api2::types::{Userid, SnapshotVerifyState};
 use crate::backup::*;
 use crate::server::WorkerTask;
 use crate::server::formatter::*;
@@ -66,13 +66,16 @@ struct FixedWriterState {
     incremental: bool,
 }
 
+// key=digest, value=(length, existance checked)
+type KnownChunksMap = HashMap<[u8;32], (u32, bool)>;
+
 struct SharedBackupState {
     finished: bool,
     uid_counter: usize,
     file_counter: usize, // successfully uploaded files
     dynamic_writers: HashMap<usize, DynamicWriterState>,
     fixed_writers: HashMap<usize, FixedWriterState>,
-    known_chunks: HashMap<[u8;32], u32>,
+    known_chunks: KnownChunksMap,
     backup_size: u64, // sums up size of all files
     backup_stat: UploadStatistic,
 }
@@ -153,7 +156,7 @@ impl BackupEnvironment {
 
         state.ensure_unfinished()?;
 
-        state.known_chunks.insert(digest, length);
+        state.known_chunks.insert(digest, (length, false));
 
         Ok(())
     }
@@ -195,7 +198,7 @@ impl BackupEnvironment {
         if is_duplicate { data.upload_stat.duplicates += 1; }
 
         // register chunk
-        state.known_chunks.insert(digest, size);
+        state.known_chunks.insert(digest, (size, true));
 
         Ok(())
     }
@@ -228,7 +231,7 @@ impl BackupEnvironment {
         if is_duplicate { data.upload_stat.duplicates += 1; }
 
         // register chunk
-        state.known_chunks.insert(digest, size);
+        state.known_chunks.insert(digest, (size, true));
 
         Ok(())
     }
@@ -237,7 +240,7 @@ impl BackupEnvironment {
         let state = self.state.lock().unwrap();
 
         match state.known_chunks.get(digest) {
-            Some(len) => Some(*len),
+            Some((len, _)) => Some(*len),
             None => None,
         }
     }
@@ -454,6 +457,47 @@ impl BackupEnvironment {
         Ok(())
     }
 
+    /// Ensure all chunks referenced in this backup actually exist.
+    /// Only call *after* all writers have been closed, to avoid race with GC.
+    /// In case of error, mark the previous backup as 'verify failed'.
+    fn verify_chunk_existance(&self, known_chunks: &KnownChunksMap) -> Result<(), Error> {
+        for (digest, (_, checked)) in known_chunks.iter() {
+            if !checked && !self.datastore.chunk_path(digest).0.exists() {
+                let mark_msg = if let Some(ref last_backup) = self.last_backup {
+                    let last_dir = &last_backup.backup_dir;
+                    let verify_state = SnapshotVerifyState {
+                        state: "failed".to_owned(),
+                        upid: self.worker.upid().clone(),
+                    };
+
+                    let res = proxmox::try_block!{
+                        let (mut manifest, _) = self.datastore.load_manifest(last_dir)?;
+                        manifest.unprotected["verify_state"] = serde_json::to_value(verify_state)?;
+                        self.datastore.store_manifest(last_dir, serde_json::to_value(manifest)?)
+                    };
+
+                    if let Err(err) = res {
+                        format!("tried marking previous snapshot as bad, \
+                                but got error accessing manifest: {}", err)
+                    } else {
+                        "marked previous snapshot as bad, please use \
+                        'verify' for a detailed check".to_owned()
+                    }
+                } else {
+                    "internal error: no base backup registered to mark invalid".to_owned()
+                };
+
+                bail!(
+                    "chunk '{}' was attempted to be reused but doesn't exist - {}",
+                    digest_to_hex(digest),
+                    mark_msg
+                );
+            }
+        }
+
+        Ok(())
+    }
+
     /// Mark backup as finished
     pub fn finish_backup(&self) -> Result<(), Error> {
         let mut state = self.state.lock().unwrap();
@@ -490,6 +534,8 @@ impl BackupEnvironment {
             }
         }
 
+        self.verify_chunk_existance(&state.known_chunks)?;
+
         // marks the backup as successful
         state.finished = true;
 
-- 
2.20.1

Re: [pbs-devel] [PATCH v4 proxmox-backup 2/2] backup: check all referenced chunks actually exist

[Dietmar Maurer]

unrelated question below:

 /// Ensure all chunks referenced in this backup actually exist.
> +    /// Only call *after* all writers have been closed, to avoid race with GC.
> +    /// In case of error, mark the previous backup as 'verify failed'.
> +    fn verify_chunk_existance(&self, known_chunks: &KnownChunksMap) -> Result<(), Error> {
> +        for (digest, (_, checked)) in known_chunks.iter() {
> +            if !checked && !self.datastore.chunk_path(digest).0.exists() {
> +                let mark_msg = if let Some(ref last_backup) = self.last_backup {
> +                    let last_dir = &last_backup.backup_dir;
> +                    let verify_state = SnapshotVerifyState {
> +                        state: "failed".to_owned(),

Why is state a String? This should be an enum instead? Please can you take a look at that? 

> +                        upid: self.worker.upid().clone(),
> +                    };
> +
> +                    let res = proxmox::try_block!{
> +                        let (mut manifest, _) = self.datastore.load_manifest(last_dir)?;
> +                        manifest.unprotected["verify_state"] = serde_json::to_value(verify_state)?;
> +                        self.datastore.store_manifest(last_dir, serde_json::to_value(manifest)?)
> +                    };

Re: [pbs-devel] [PATCH v4 proxmox-backup 2/2] backup: check all referenced chunks actually exist

[Thomas Lamprecht]

On 9/15/20 8:09 AM, Dietmar Maurer wrote:
> unrelated question below:
> 
>  /// Ensure all chunks referenced in this backup actually exist.
>> +    /// Only call *after* all writers have been closed, to avoid race with GC.
>> +    /// In case of error, mark the previous backup as 'verify failed'.
>> +    fn verify_chunk_existance(&self, known_chunks: &KnownChunksMap) -> Result<(), Error> {
>> +        for (digest, (_, checked)) in known_chunks.iter() {
>> +            if !checked && !self.datastore.chunk_path(digest).0.exists() {
>> +                let mark_msg = if let Some(ref last_backup) = self.last_backup {
>> +                    let last_dir = &last_backup.backup_dir;
>> +                    let verify_state = SnapshotVerifyState {
>> +                        state: "failed".to_owned(),
> 
> Why is state a String? This should be an enum instead? Please can you take a look at that? 

It really should be an enum, no idea why I did not made it one to begin with.

Re: [pbs-devel] [PATCH v4 proxmox-backup 2/2] backup: check all referenced chunks actually exist

[Dietmar Maurer]

We modify the manifest from several locations now:

src/backup/verify.rs
src/api2/admin/datastore.rs (set_notes)

and here:

> +                    let res = proxmox::try_block!{
> +                        let (mut manifest, _) = self.datastore.load_manifest(last_dir)?;
> +                        manifest.unprotected["verify_state"] = serde_json::to_value(verify_state)?;
> +                        self.datastore.store_manifest(last_dir, serde_json::to_value(manifest)?)
> +                    };
> +


So we need some kind of locking!

[pbs-devel] applied: [PATCH v4 proxmox-backup 1/2] backup: check verify state of previous backup before allowing reuse

[Dietmar Maurer]

applied

[pbs-devel] applied: [PATCH v4 proxmox-backup 2/2] backup: check all referenced chunks actually exist

[Dietmar Maurer]

applied (expecting further cleanups)