backup: use shared flock for base snapshot

To allow other reading operations on the base snapshot as well. No
semantic changes with this patch alone, as all other locks on snapshots
are exclusive.

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

diff --git a/src/api2/backup.rs b/src/api2/backup.rs
index 8a2a240964f9c53c23c72e3d44bc0c6a6f72b372..8b2b0e1a4f89f2320316a15a1dba2dd1a9c33ffc 100644 (file)
--- a/src/api2/backup.rs
+++ b/src/api2/backup.rs
@@ -16,7 +16,7 @@ use crate::backup::*;
 use crate::api2::types::*;
 use crate::config::acl::PRIV_DATASTORE_BACKUP;
 use crate::config::cached_user_info::CachedUserInfo;
-use crate::tools::fs::lock_dir_noblock;
+use crate::tools::fs::lock_dir_noblock_shared;
 
 mod environment;
 use environment::*;
@@ -144,7 +144,7 @@ async move {
 
         // lock last snapshot to prevent forgetting/pruning it during backup
         let full_path = datastore.snapshot_path(&last.backup_dir);
-        Some(lock_dir_noblock(&full_path, "snapshot", "base snapshot is already locked by another operation")?)
+        Some(lock_dir_noblock_shared(&full_path, "snapshot", "base snapshot is already locked by another operation")?)
     } else {
         None
     };

diff --git a/src/tools/fs.rs b/src/tools/fs.rs
index 5aaaecda75b2b55b3dbadcd9e436f1f859aa0467..72a530d8ed976e09645877e128e1466605c6de15 100644 (file)
--- a/src/tools/fs.rs
+++ b/src/tools/fs.rs
@@ -265,11 +265,31 @@ impl Default for FSXAttr {
     }
 }
 
+/// Attempt to acquire a shared flock on the given path, 'what' and
+/// 'would_block_message' are used for error formatting.
+pub fn lock_dir_noblock_shared(
+    path: &std::path::Path,
+    what: &str,
+    would_block_msg: &str,
+) -> Result<DirLockGuard, Error> {
+    do_lock_dir_noblock(path, what, would_block_msg, false)
+}
 
+/// Attempt to acquire an exclusive flock on the given path, 'what' and
+/// 'would_block_message' are used for error formatting.
 pub fn lock_dir_noblock(
     path: &std::path::Path,
     what: &str,
     would_block_msg: &str,
+) -> Result<DirLockGuard, Error> {
+    do_lock_dir_noblock(path, what, would_block_msg, true)
+}
+
+fn do_lock_dir_noblock(
+    path: &std::path::Path,
+    what: &str,
+    would_block_msg: &str,
+    exclusive: bool,
 ) -> Result<DirLockGuard, Error> {
     let mut handle = Dir::open(path, OFlag::O_RDONLY, Mode::empty())
         .map_err(|err| {
@@ -278,7 +298,7 @@ pub fn lock_dir_noblock(
 
     // acquire in non-blocking mode, no point in waiting here since other
     // backups could still take a very long time
-    proxmox::tools::fs::lock_file(&mut handle, true, Some(std::time::Duration::from_nanos(0)))
+    proxmox::tools::fs::lock_file(&mut handle, exclusive, Some(std::time::Duration::from_nanos(0)))
         .map_err(|err| {
             format_err!(
                 "unable to acquire lock on {} directory {:?} - {}", what, path,