netfs_perform_write(9)

💅 netfs_perform_write — like, the Kernel API Manual girlies know 💅

okay so bestie, today's main character is netfs_perform_write(9) from the Kernel API Manual, and she is literally out here copying data into the pagecache. no cap. let's get into it 🫶

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✨ NAME ✨

netfs_perform_write — copy data into the pagecache. that's it, that's the vibe 🎀

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🌸 SYNOPSIS 🌸

ssize_t netfs_perform_write (struct kiocb *iocb , struct iov_iter *iter
, struct netfs_group *netfs_group );

look at her. three args. iconic behavior only 💖

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🦋 ARGUMENTS 🦋

• iocb — the operation parameters, aka the whole entire vibe of the write. she's the blueprint ✨
• iter — the source buffer. this is where the data is actually coming from, bestie 🍓
• netfs_group — the grouping for dirty folios (eg. ceph snaps). yes she groups. she organizes. she's that girl 💅

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🔥 DESCRIPTION 🔥

So what does she do? She copies data into pagecache folios attached to the inode specified by iocb. Simple. Clean. Gorgeous. 🌈

⚠️ But listen — the caller must hold appropriate inode locks. Do not skip this. This is not a suggestion, this is a requirement, and she WILL know if you skipped it 😭

Now for the lore 🧚 Dirty folios get tagged with a netfs_folio struct if they're not up to date — that tag is there to indicate the range modified. Like a little sticky note saying "hey, this part changed" 🎀

Dirty folios may also be tagged with a netfs-specific grouping, such that data from an old group gets flushed before a new one is started. old group out, new group in. slay 💀✨

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💜 SEE ALSO 💜

• Kernel file ./fs/netfs/buffered_write.c
• netfs_buffered_write_iter_locked(9)
• netfs_file_write_iter(9)

go read those too, bestie, you won't regret it 👑

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and that's the whole page, fr fr 🫶 this little gem lives in ./fs/netfs, dated October 2026, and she goes by netfs_perform_write(9) — mwah, no notes, periodt 💋🌸