filemap_get_folio(9)

💅 filemap_get_folio — the Kernel API Manual, bestie edition ✨

okay so this is filemap_get_folio(9) from the Kernel API Manual, and honestly? it's giving "small function, huge main character energy" 🎀 let's get into it.

---

🌸 NAME 🌸

filemap_get_folio — find and get a folio. that's it. that's the whole vibe. 💖

---

✨ SYNOPSIS ✨

struct folio * filemap_get_folio (struct address_space *mapping ,
pgoff_t index );

literally two args, no cap. 🫶

---

🦋 ARGUMENTS 🦋

• mapping — the address_space you're searching through. this is the lookup zone, the search space, the place where the folios live. 🔍
• index — the page index. yeah. the index. of the page. that one. 📖

---

💜 DESCRIPTION 💜

so what it does — it looks up the page cache entry at mapping & index. cute, right? and if a folio is actually present there? it gets returned to you with an increased refcount 👑 so like, bestie, you now own a reference. hold onto it responsibly. that's the whole thing. 💅

---

🔥 RETURN 🔥

you get either:

• a folio 💖 — slay, it was there
• or ERR_PTR(-ENOENT) 😭 — if there's no folio in the cache for this index

and important: it will not return a shadow, swap or DAX entry. periodt. not doing it. don't ask. 💀

---

🌈 SEE ALSO 🌈

Kernel file ./include/linux/pagemap.h, plus this absolutely iconic lineup of related pages (iykyk):

• filemap_set_wb_err(9)
• filemap_check_wb_err(9)
• filemap_sample_wb_err(9)
• file_sample_sb_err(9)
• mapping_set_error(9)
• mapping_set_large_folios(9)
• mapping_align_index(9)
• mapping_pmd_folio_support(9)
• folio_flush_mapping(9)
• folio_inode(9)
• folio_attach_private(9)
• folio_change_private(9)
• folio_detach_private(9)
• fgf_t(9)
• fgf_set_order(9)
• write_begin_get_folio(9)
• filemap_lock_folio(9)
• filemap_grab_folio(9)
• find_get_page(9)
• find_lock_page(9)
• find_or_create_page(9)
• grab_cache_page_nowait(9)
• folio_next_index(9)
• folio_next_pos(9)
• folio_file_page(9)
• folio_contains(9)
• page_pgoff(9)
• folio_pos(9)
• linear_page_delta(9)
• linear_page_index(9)
• linear_anon_page_index(9)
• folio_trylock(9)
• folio_lock(9)
• lock_page(9)
• folio_lock_killable(9)
• filemap_range_needs_writeback(9)
• struct readahead_control(9)
• page_cache_sync_readahead(9)
• page_cache_async_readahead(9)
• readahead_folio(9)
• readahead_pos(9)
• readahead_length(9)
• readahead_index(9)
• readahead_count(9)
• readahead_batch_length(9)
• folio_mkwrite_check_truncate(9)
• i_blocks_per_folio(9)

like, that's a whole friend group right there 🧚💜

---

🫶 quick reminder bestie: the refcount is increased when a folio comes back to you. that's the deal. don't fumble it.

---

and that's the page!! sourced from ./include/linux, dated October 2026, filed under filemap_get_folio(9) — mwah, go read some folios 💋🌸⭐