shmem_recalc_inode(9)

✨ NAME ✨

Okay bestie, this is shmem_recalc_inode(9) from the Kernel API Manual, and it does exactly what the name says: recalculate the block usage of an inode. Periodt. 💅

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🌸 SYNOPSIS 🌸

bool shmem_recalc_inode (struct inode *inode , long alloced , long
       swapped );

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🎀 ARGUMENTS 🎀

• inode — the inode we’re recalculating, no cap.
• alloced — the change in number of pages allocated to inode.
• swapped — the change in number of pages swapped from inode.

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💅 DESCRIPTION 💅

So here’s the tea: we have to calculate the free blocks since the mm can drop undirtied hole pages behind our back. 😭

But normally, it’s giving this exact equation:

info->alloced == inode->i_mapping->nrpages + info->swapped

So the mm freed amount is literally:

info->alloced - (inode->i_mapping->nrpages + info->swapped)

That’s the whole math vibe, iykyk. 🧮✨

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🫶 RETURN 🫶

It returns true if swapped was incremented from 0 — specifically for shmem_writeout. Slay. ✅

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🔥 SEE ALSO 🔥

The kernel file lore lives in ./mm/shmem.c, and the squad to check out is:

• shmem_writeout(9)
• shmem_get_folio(9)
• shmem_kernel_file_setup(9)
• shmem_file_setup(9)
• shmem_file_setup_with_mnt(9)
• shmem_zero_setup(9)
• shmem_zero_setup_desc(9)
• shmem_read_folio_gfp(9)

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k bye bestie — source/version info is ./mm, dated October 2026, mwah 💋✨