mapping_align_index(9)

💖 mapping_align_index(9) — the Kernel API Manual glow-up 💖

okay so you're reading the Kernel API Manual, page mapping_align_index(9), and honestly? you picked a short one. iconic of you. let's go 🫶

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✨ NAME ✨

mapping_align_index — align the index for this mapping. that's it. that's the whole vibe check. 💅

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🌸 SYNOPSIS 🌸

pgoff_t mapping_align_index (const struct address_space *mapping ,
pgoff_t index );

look at her. two args, one return type, zero drama. copy it exactly bestie, i'm not kidding around with signatures. ⭐

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🎀 ARGUMENTS 🎀

• mapping — the address_space. yes, the whole address space. she's the main character here. 👑
• index — the page index. that's the number you're asking about. 🔥

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🦋 DESCRIPTION 🦋

okay so here's the tea: the index of a folio must be naturally aligned. like, non-negotiable, it's giving house rules. 🏠✨

so if you're adding a shiny new folio to the page cache and you're sitting there like "wait… what index do i even give it 😭" — you call this function. that's literally what it's for. it hands you the aligned index so you don't have to think about it. no cap, that's the entire job. 💜

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🌈 SEE ALSO 🌈

the kernel file ./include/linux/pagemap.h says hi, and it brought friends. so many friends. all of them, right here, no skips: 🙈

• 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_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_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. go say hi. 🍓

lowkey if you only remember one thing: the folio index has to be naturally aligned, and this function is the one that makes it so. everything else is lore. 💀

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and that's the page bestie!! sourced from ./include/linux, dated October 2026, straight out of the Kernel API Manual (version vibes: the one you're holding rn). stay aligned, stay iconic, mwah 💋🧚‍♀️💜