There is a disparency of behavior under Linux & Windows about
the returned error when trying to rename a non existant path.
err := os.Rename("/path/does/not/exist", "/tmp/copy")
Linux:
isSysErrNotDir(err) = false
os.IsNotExist(err) = true
Windows:
isSysErrNotDir(err) = true
os.IsNotExist(err) = true
ENOTDIR in Linux is returned when the destination path
of the rename call contains a file in one of the middle
segments of the path (e.g. /tmp/file/dst, where /tmp/file
is an actual file not a directory)
However, as shown above, Windows has more scenarios when
it returns ENOTDIR. For example, when the source path contains
an inexistant directory in its path.
In that case, we want errFileNotFound returned and not
errFileAccessDenied, so this commit will add a further check to close
the disparency between Windows & Linux.
Calling ListMultipartUploads fails if an upload is aborted while a
part is being uploaded because the directory for the upload exists
(since fsRenameFile ends up calling os.MkdirAll) but the meta JSON file
doesn't. To fix this we make sure an upload hasn't been aborted during
PutObjectPart by checking the existence of the directory for the upload
while moving the temporary part file into it.
In scenario 1
```
- bucket/object-prefix
- bucket/object-prefix/object
```
Server responds with `XMinioParentIsObject`
In scenario 2
```
- bucket/object-prefix/object
- bucket/object-prefix
```
Server responds with `XMinioObjectExistsAsDirectory`
Fixes#6566
Under any concurrent removeObjects in progress
might have removed the parents of the same prefix
for which there is an ongoing putObject request.
An inconsistent situation may arise as explained
below even under sufficient locking.
PutObject is almost successful at the last stage when
a temporary file is renamed to its actual namespace
at `a/b/c/object1`. Concurrently a RemoveObject is
also in progress at the same prefix for an `a/b/c/object2`.
To create the object1 at location `a/b/c` PutObject has
to create all the parents recursively.
```
a/b/c - os.MkdirAll loops through has now created
'a/' and 'b/' about to create 'c/'
a/b/c/object2 - at this point 'c/' and 'object2'
are deleted about to delete b/
```
Now for os.MkdirAll loop the expected situation is
that top level parent 'a/b/' exists which it created
, such that it can create 'c/' - since removeObject
and putObject do not compete for lock due to holding
locks at different resources. removeObject proceeds
to delete parent 'b/' since 'c/' is not yet present,
once deleted 'os.MkdirAll' would receive an error as
syscall.ENOENT which would fail the putObject request.
This PR tries to address this issue by implementing
a safer/guarded approach where we would retry an operation
such as `os.MkdirAll` and `os.Rename` if both operations
observe syscall.ENOENT.
Fixes#5254
