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Deleting a big file froze the desktop for seconds: ext2 FreeBlock did 4 synchronous disk I/Os per data block (bitmap + BGDT read/write), and the file manager deleted single files inline on the desktop main thread. - Ext2: batch block frees per block group; keep the bitmap resident, clear bits in memory, flush bitmap + BGDT once per group transition. Also covers the truncate-on-overwrite path. - Ext2: refuse to mount volumes with block size > 4096; temp buffers throughout the driver are single 4 KiB pages, so larger blocks would overflow them (our mkfs always uses 4K). - Files: route single-file deletes past 4 MiB to the background worker + progress dialog; refuse (instead of stalling inline) when another file operation already owns the worker. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>