Check available disk space before writing objects

[deepjoy]

Description

The filesystem storage backend does not currently verify that there is enough disk space before writing an object. Large uploads could fail partway through, leaving partial files on disk.

Location

• src/storage/filesystem.rs:152

Details

The put() method should check available disk space before starting a write and reject the request with an appropriate S3 error if the object would not fit.

Things to consider:

• Use statvfs or equivalent to check free space
• Account for the incoming Content-Length header
• Consider a configurable low-watermark threshold
• Handle the case where Content-Length is unknown (chunked uploads)
• Clean up partial writes on failure (may already be handled)

Acceptance Criteria

• Check available disk space before starting a write in put()
• Return an appropriate S3 error (e.g., InsufficientStorage or similar) when space is low
• Add configurable low-watermark threshold
• Ensure partial files are cleaned up on failure