backup: index readers: drop useless shared lock

This is only acquired in those two methods, both as shared. So it has
no use.

It seems, that it was planned in the past that the index deletion
should take the exclusive, while read and write takes the shared
flock on the index, as one can guess from the lock comments in commit
0465218953

But then later, in commit c8ec450e37)
the documented semantics where changed to use a temp file and do an
atomic rename instead for atomicity.

The reader shared flock on the index file was done inbetween,
probably as preparatory step, but was not removed again when strategy
was changed to using the file rename instead.

Do so now, to avoid confusion of readers and a useless flock.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/backup/dynamic_index.rs

@@ -90,12 +90,6 @@ impl DynamicIndexReader {
     }
 
     pub fn new(mut file: std::fs::File) -> Result<Self, Error> {
-        if let Err(err) =
-            nix::fcntl::flock(file.as_raw_fd(), nix::fcntl::FlockArg::LockSharedNonblock)
-        {
-            bail!("unable to get shared lock - {}", err);
-        }
-
         // FIXME: This is NOT OUR job! Check the callers of this method and remove this!
         file.seek(SeekFrom::Start(0))?;
 

src/backup/fixed_index.rs

@@ -65,12 +65,6 @@ impl FixedIndexReader {
     }
 
     pub fn new(mut file: std::fs::File) -> Result<Self, Error> {
-        if let Err(err) =
-            nix::fcntl::flock(file.as_raw_fd(), nix::fcntl::FlockArg::LockSharedNonblock)
-        {
-            bail!("unable to get shared lock - {}", err);
-        }
-
         file.seek(SeekFrom::Start(0))?;
 
         let header_size = std::mem::size_of::<FixedIndexHeader>();