Fix post-remount soft-lockup by persisting new directory block init#90
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RoyWFHuang wants to merge 1 commit into
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Fix post-remount soft-lockup by persisting new directory block init#90RoyWFHuang wants to merge 1 commit into
RoyWFHuang wants to merge 1 commit into
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simplefs_get_new_ext() initializes each new directory block with files[0].nr_blk = SIMPLEFS_FILES_PER_BLOCK but released the buffer without mark_buffer_dirty(), so the init was never written back. After a remount the block reads back all-zero (nr_blk == 0) and the "_fi += nr_blk" scan in __file_lookup() never advances -> kernel soft-lockup.
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This was referenced Jun 20, 2026
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Root cause
get_free_blocks() (bitmap.h) zeroes each of the 8 blocks (SIMPLEFS_MAX_BLOCKS_PER_EXTENT) of a new extent and sync_dirty_buffer()s them → on disk every block is all-zero.
simplefs_get_new_ext() (inode.c) writes files[0].nr_blk = SIMPLEFS_FILES_PER_BLOCK into each block, but releases the buffer with brelse() only — no mark_buffer_dirty() — so the initialization lives only in the page cache and is never written back.
simplefs_create() inserts the file into a single block and marks only that block (and the ei_block) dirty. The remaining blocks of the extent are never dirtied → they stay all-zero on disk.
On unmount, simplefs_put_super() does sync_blockdev(), flushes only dirty buffers(drops the cached). On remount the blocks are read from disk as {inode: 0, nr_blk: 0}.
Closes #89
Summary by cubic
Persist directory block initialization by marking new dir block buffers dirty in
simplefs_get_new_ext(), preventing post-remount soft-lockups.mark_buffer_dirty(bh)after settingfiles[0].nr_blk = SIMPLEFS_FILES_PER_BLOCKso the init is written to disk.nr_blk == 0, which caused__file_lookup()to loop and soft-lock the kernel.Written for commit a75f22e. Summary will update on new commits.