replace_page_cache_folio(9)

💖 replace_page_cache_folio 💖

okay bestie, welcome to the kernel API manual for replace_page_cache_folio(9) — she's a little function from the <pink>Kernel API Manual</pink>, and honestly? she's iconic for one specific reason that we'll get to. buckle up 🎀

---

🌸 NAME 🌸

replace_page_cache_folio — swap out a pagecache folio for a shiny brand-new one, no cap ✨

---

🦋 SYNOPSIS 🦋

void replace_page_cache_folio (struct folio *old , struct folio *new );

that's it. that's the whole signature. two folios, one job 💅

---

🎀 ARGUMENTS 🎀

• old — the folio getting replaced. she's being asked to step aside 👋
• new — the folio doing the replacing. she's the understudy and she's ABOUT to go on 🌟

---

⭐ DESCRIPTION ⭐

so like, what does she actually do? This function replaces a folio in the pagecache with a new one. periodt. 🫶

On success it acquires the pagecache reference for the new folio and drops it for the old folio — so the refcount handoff is handled for you, which is lowkey a serve 💅

Both the old and new folios must be locked. fr fr. do not skip this. locked folios only, bestie 🔒

Also — and this is the part people forget — this function does not add the new folio to the LRU. The caller must do that. she does not do it for you, she is not your mom 🙈

The remove + add is atomic. and the absolute main-character flex: this function cannot fail. no return value, no error path, no "whoops try again". it literally cannot miss. 😭🔥

---

🌈 SEE ALSO 🌈

okay this list is LONG but we do not skip a single one, every sibling gets their moment 👑

• Kernel file ./mm/filemap.c
• filemap_remove_folio(9)
• filemap_fdatawrite_range(9)
• filemap_flush_range(9)
• filemap_flush(9)
• filemap_range_has_page(9)
• filemap_fdatawait_range(9)
• filemap_fdatawait_range_keep_errors(9)
• file_fdatawait_range(9)
• filemap_fdatawait_keep_errors(9)
• filemap_write_and_wait_range(9)
• file_check_and_advance_wb_err(9)
• file_write_and_wait_range(9)
• softleaf_entry_wait_on_locked(9)
• folio_put_wait_locked(9)
• folio_unlock(9)
• folio_end_read(9)
• folio_end_private_2(9)
• folio_wait_private_2(9)
• folio_wait_private_2_killable(9)
• folio_end_writeback_no_dropbehind(9)
• folio_end_writeback(9)
• __folio_lock(9)
• page_cache_next_miss(9)
• page_cache_prev_miss(9)
• __filemap_get_folio_mpol(9)
• find_get_entries(9)
• find_lock_entries(9)
• filemap_get_folios(9)
• filemap_get_folios_contig(9)
• filemap_get_folios_tag(9)
• filemap_get_folios_dirty(9)
• filemap_read(9)
• generic_file_read_iter(9)
• filemap_splice_read(9)
• mapping_seek_hole_data(9)
• filemap_fault(9)
• read_cache_folio(9)
• mapping_read_folio_gfp(9)
• read_cache_page_gfp(9)
• __generic_file_write_iter(9)
• generic_file_write_iter(9)
• filemap_release_folio(9)
• filemap_invalidate_inode(9)
• filemap_cachestat(9)

---

✨ that's the whole page, bestie ✨ this one lives in ./mm, it's dated October 2026, and it's filed under replace_page_cache_folio(9). go forth and lock your folios 💜🦋💅