folio_end_private_2(9)

💅 folio_end_private_2(9) — a Kernel API Manual moment

okay so bestie, welcome to the <pink>Kernel API Manual</pink> ✨ today's main character is folio_end_private_2(9) and honestly she's a little cleanup queen with a very specific job 🎀

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🌸 NAME

folio_end_private_2 — clears PG_private_2 and wakes up literally anyone who's been waiting on it 💖

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✨ SYNOPSIS

void folio_end_private_2 (struct folio *folio );

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🫶 ARGUMENTS

• folio — the folio. that's it. that's the whole argument. she's low maintenance 💅

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🔥 DESCRIPTION

okay so what she does is: clear the PG_private_2 bit on a folio, and wake up any sleepers that are waiting on it 😴➡️😳 and bestie, the folio reference that was being held for PG_private_2 being set? yeah, that gets released too. no lingering attachments, we love a clean exit 🦋

fr fr, this is, for example, used when a netfs folio is being written to a local disk cache — which is what allows writes to the cache for the same folio to be serialised. the way that works is genuinely iconic ngl 👑

not me explaining bit flags and disk cache serialisation at the same time — but that's literally the whole vibe, iykyk 🧚

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👑 SEE ALSO

like, the whole extended friend group 💜 — kernel file ./mm/filemap.c and honestly so many siblings:

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_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)

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and that's the whole page bestie, you ate that 🍓

signing off from ./mm, dated October 2026 — mwah 💋