truncate_pagecache(9)

✨ truncate_pagecache — the Kernel API Manual tea ☕💅

Okay so bestie, welcome to the Kernel API Manual entry for truncate_pagecache(9), and honestly? This one is a whole vibe. It's the function that unmaps and removes pagecache that has been truncated. Iconic behavior, no cap. 🎀

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✨ SYNOPSIS ✨

void truncate_pagecache (struct inode *inode , loff_t newsize );

That's it. That's the whole signature. Short, sweet, and it will absolutely ruin your day if you call it wrong. 🫶

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🌸 ARGUMENTS 🌸

• inode — the inode. Yeah bestie, it's literally just an inode. That's the whole description. Go off I guess. 💀
• newsize — the new file size. This is the size you're shrinking (or, like, resizing) down to. Main character energy. 👑

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💖 DESCRIPTION 💖

So here's the situation. The inode's new i_size must already be written before truncate_pagecache is called. Like, before. Not after. Before. The function is not out here doing that for you, it's not your assistant, it's your colleague. 🙈

This function should typically be called before the filesystem releases resources associated with the freed range — for example, before it deallocates blocks. The way that this matters is honestly so real: doing it in that order means pagecache will always stay logically coherent with the on-disk format. Slay. 💅

And because of that ordering, the filesystem doesn't have to deal with cursed situations — like writepage being called for a page that has already had its underlying blocks deallocated. Nobody wants that. That's a vibe check failure of the highest order. 😭

ngl, get the ordering wrong here and you're in for a bad time. Write i_size first, truncate the pagecache second, release resources third. Periodt. ⭐

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🦋 SEE ALSO 🦋

Kernel file ./mm/truncate.c, plus all these besties right here:

• folio_invalidate(9)
• mapping_evict_folio(9)
• truncate_inode_pages_range(9)
• truncate_inode_pages(9)
• truncate_inode_pages_final(9)
• mapping_try_invalidate(9)
• invalidate_mapping_pages(9)
• invalidate_inode_pages2_range(9)
• invalidate_inode_pages2(9)
• truncate_setsize(9)
• pagecache_isize_extended(9)
• truncate_pagecache_range(9)

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💫 and that's the whole page, bestie 💫

This little gem lives in the source ./mm, and the version stamp on it is October 2026 for truncate_pagecache(9). Go forth, truncate responsibly, and remember: i_size first. Always. 🍓🧚💜