softleaf_en...it_on_locked(9)

💖 softleaf_entry_wait_on_locked(9) — the kernel API manual, but make it make sense 💖

okay so bestie, pull up a chair, because we're reading a kernel API manual page together and honestly? it's giving "waiting room energy" but in the good way. this is the softleaf_en...it_on_locked(9) page (yes the header truncates it like that, the kernel is dramatic 💅), from the Kernel API Manual.

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✨ NAME ✨

softleaf_entry_wait_on_locked — literally just: wait for a migration entry or a device_private entry to be removed. that's the whole vibe. it waits. it's patient. main character energy 🕰️

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🌸 SYNOPSIS 🌸

void softleaf_entry_wait_on_locked (softleaf_t entry , spinlock_t *ptl
);

yep that's the signature, copy it exactly, no cap 🫶

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🎀 ARGUMENTS 🎀

• entry — a migration swap entry or a device_private swap entry. that's the thing we're waiting on, bestie.
• ptl — an already locked ptl. heads up: this function will drop the lock. it takes the lock from your hands and lets go of it, so don't go assuming you still hold it after, okay? 😭

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🦋 DESCRIPTION 🦋

So here's the tea ☕: this function waits for a migration entry that references the given page, or a device_private entry that references a dvice_private page (and yes, that's literally how it's spelled in the original — we don't fix, we report 🙈), to be unlocked.

It is equivalent to:

folio_put_wait_locked(folio, TASK_UNINTERRUPTIBLE)

...with one iconic little difference: this one can be called without taking a reference on the page. obsessed. instead, you should call it while holding the ptl for the entry that references the page. that's the whole trick ✨

It returns after unlocking the ptl. so like, the unlock already happened by the time you get control back. not me warning you twice 💀

It follows the same logic as folio_wait_bit_common, so if you want the deep lore, go read the comments there. iykyk 📖

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👑 SEE ALSO 👑

Kernel file ./mm/filemap.c, plus this whole friend group right here — every single one, no skips:

• 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)
• 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)

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🌈 quick reminder bestie: ptl comes in locked, and this function drops it. that's not a bug, that's the whole bit. don't double-unlock, don't touch it after. periodt 💅

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and that's the page!! 💜 source is ./mm, dated October 2026, and it lives in the Kernel API Manual — go forth, wait on your locked entries responsibly, and slay 🧚‍♀️✨🌸