readahead_index(9)

💅 readahead_index — like, the kernel API manual, but make it make sense 🎀

okay bestie, so the header says readahead_index(9) and the manual is literally called Kernel API Manual — yes, the whole vibe. anyway. we're in the 9 section, this is kernel-API territory, and this little function is here to hand you a number. that's it. that's the whole gig. and honestly? she serves. 💖

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✨ NAME ✨

readahead_index — the index of the first page in this readahead request. that's the one. the index. of the first page. in this readahead request. no cap, it's exactly what it says on the tin 🫶

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🌸 SYNOPSIS 🌸

pgoff_t readahead_index (const struct readahead_control *rac );

the way this signature is just sitting there being all pgoff_t and taking a const struct readahead_control * — like yes, const-correct king, we love to see it 👑

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🦋 ARGUMENTS 🦋

• rac — the readahead request. that's it. that's the whole parameter list. she takes one (1) argument and she's not sorry about it 💅

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🌈 SEE ALSO 🌈

okay so this is the part where I hold your hand, because there is a lot of family here. first up, the file she lives in:

Kernel file ./include/linux/pagemap.h — that's home base, that's where the whole crew hangs out 🏠

and then the extended friend group, alphabetically-ish, all of them (9) pages, all of them worth a peek:

• 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_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_count(9)
• readahead_batch_length(9)
• folio_mkwrite_check_truncate(9)
• i_blocks_per_folio(9)

like, that's the whole group chat. read them, love them, cite them in your patch comments. iykyk 💀✨

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lowkey a reminder: this page tells you what readahead_index gives you (the index of the first page of the request) and which request it reads it from (rac). it does not promise you anything else, bestie, so don't go inventing behaviour. 🙈

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and that's the page!! brought to you by ./include/linux 📁, dated October 2026 🗓️, filed under readahead_index(9) — mwah, iconic, no notes. 💜🎀🧚