PARTIAL BACKUP AND RESTORATION OF A STRUCT TTM_TT.(9)

💖 NAME 💖

Partial back...ruct ttm_tt.(9) — the partial backup and restoration of a struct ttm_tt ✨ (this is a Kernel API page, bestie, so buckle up 🎀)

🌸 DESCRIPTION 🌸

okay so first things first: swaps don't always go your way 😭 Swapout using ttm_backup_backup_folio and swapin using ttm_backup_copy_page may fail — like, actually. The former (swapout) most likely bails because of lack of swap-space or memory, and the latter (swapin) bails because of lack of memory or because of signal interruption during waits. no cap, it just happens 💀

But here's the slay: backup failure is easily handled by using a ttm_tt pages vector that holds both backup handles and page pointers 🫶 that's the whole trick, iykyk. And you have to keep that in mind in two places:

• when you're restoring such a ttm_tt from backup 🦋
• when you're freeing it while it's backed up 🦋

When restoring, for simplicity, new pages are actually allocated from the pool, and the contents of any old pages are copied in, and then the old pages are released. that's the whole flow, periodt ✨

🧚 restoration failures, aka the plot twist

For restoration failures, the struct ttm_pool_tt_restore holds sufficient state to be able to resume an interrupted restore 👑 and that structure is freed once the restoration is complete. and if the struct ttm_tt is destroyed while there is a valid struct ttm_pool_tt_restore attached? that is also properly taken care of 💅 no leaks, no drama, we love to see it.

lowkey the takeaway: backups can fail, restores can get interrupted, and the bookkeeping in struct ttm_pool_tt_restore is what saves you 😌

⭐ SEE ALSO ⭐

Kernel file ./drivers/gpu/drm/ttm/ttm_pool.c 🍓 plus the whole friend group:

• struct ttm_pool_dma(9)
• struct ttm_pool_alloc_state(9)
• struct ttm_pool_tt_restore(9)
• ttm_pool_free_range(9)
• ttm_pool_alloc(9)
• ttm_pool_restore_and_alloc(9)
• ttm_pool_free(9)
• ttm_pool_drop_backed_up(9)
• ttm_pool_backup(9)
• ttm_pool_init(9)
• ttm_pool_synchronize_shrinkers(9)
• ttm_pool_fini(9)
• ttm_pool_debugfs(9)
• ttm_pool_mgr_init(9)
• ttm_pool_mgr_fini(9)

sign-off time 🎀 this little masterpiece lives in ./drivers/gpu/drm/ttm, dated October 2026, and it's part of the Kernel API Manual — go read the pool docs bestie, they ate 💜