filemap_release_folio(9)

✨ filemap_release_folio(9) ✨

okay so real talk, this is a page straight out of the Kernel API Manual — filemap_release_folio(9) — and it's literally about letting go of the extra little secrets a folio is holding onto. bestie, this is the breakup talk of the mm subsystem 💔✨

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🌸 NAME 🌸

filemap_release_folio — release fs-specific metadata on a folio. that's it, that's the whole vibe: folio says "i'm done", and this function helps it drop the extra stuff (filesystem-specific metadata) it was clinging to. 🎀

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🦋 SYNOPSIS 🦋

bool filemap_release_folio (struct folio *folio , gfp_t gfp );

she takes two things and gives you back a bool. iconic signature ngl 💅

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💖 ARGUMENTS 💖

• folio — The folio which the kernel is trying to free. like, the actual main character folio that's about to get yeeted out of memory 🫶
• gfp — Memory allocation flags (and I/O mode). yes, it's the flag bag — it tells you whether I/O is allowed and whether you're allowed to block. details below, keep reading 👀

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🧚 DESCRIPTION 🧚

So the address_space is trying to release any data attached to a folio — presumably the stuff chilling at folio->private. that's the whole mission: free the folio, let go of whatever extra baggage it stored in private. 🎒➡️🗑️

This will also be called if the private_2 flag is set on a page. that flag is basically a little sticky note saying "hey, this folio has other metadata associated with it too" — so yeah, this gets invoked then as well. iykyk. 📝

And the gfp argument? she's the one specifying the rules of the call, specifically:

• whether I/O may be performed to release this page — that's __GFP_IO
• whether the call may block — that's __GFP_RECLAIM & __GFP_FS

so lowkey gfp is the vibe check for "can we do I/O?" and "are we allowed to sleep here?" 😴🔥

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⭐ RETURN ⭐

• true if the release was successful 🎉
• otherwise false 😭

periodt. that's the whole return contract.

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🌈 SEE ALSO 🌈

the whole friend group, no cap — all from the 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)
• replace_page_cache_folio(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_invalidate_inode(9)
• filemap_cachestat(9)

like, the entire mm squad showed up to the group chat 😭💜

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ok but for real — this page lives in ./mm, dated October 2026. so when you're citing her, that's the receipts. 🫶✨ 🎀