fscache_begin_volume_access(9)

fscache_begin_volume_access(9) — Kernel API Manual energy ✨

okay so bestie, this is the Kernel API Manual page for fscache_begin_volume_access — and yes, I’m folding the manual name right into the intro because copying a header line is not the move 💅. This one is literally about pinning a cache so a volume can be accessed, and it’s giving kernel-internals main character energy 🔥.

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💖 NAME 💖

fscache_begin_volume_access — pin a cache so a volume can be accessed 🎀

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✨ SYNOPSIS ✨

the signature, verbatim, no edits, no cap:

bool fscache_begin_volume_access (struct fscache_volume *volume , struct
       fscache_cookie *cookie , enum fscache_access_trace why );

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🎀 ARGUMENTS 🎀

• volume — the volume cookie 🍪
• cookie — a datafile cookie for a tracing reference, or NULL 🫶
• why — an indication of the circumstances of the access, for tracing 🔍

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🦋 DESCRIPTION 🦋

It tries to pin the cache so it won’t go away whilst we’re accessing a volume, and it returns true if successful. Here’s the whole flow, bestie:

1. If the cache tests as not live (state is not FSCACHE_CACHE_IS_ACTIVE), then we return false to indicate access was not permitted. no access for you 🙈
2. If the cache tests as live, then we increment the volume’s n_accesses count and then recheck the cache liveness, ending the access if it ceased to be live.
3. When we end the access, we decrement the volume’s n_accesses and wake up any waiters if it reaches 0.
4. Whilst the cache is caching, the volume’s n_accesses is kept artificially incremented to prevent wakeups from happening.
5. When the cache is taken offline, the state is changed to prevent new accesses, the volume’s n_accesses is decremented and we wait for it to become 0.

The datafile cookie and the why indicator are merely provided for tracing purposes. that’s it, that’s the tea ☕.

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🌈 SEE ALSO 🌈

Kernel file ./fs/netfs/fscache_volume.c — yes, that exact path, bestie — plus fscache_end_volume_access(9) and fscache_withdraw_volume(9) 💜

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and that’s the whole page 🫶 — source/version ./fs/netfs, date October 2026, and the title is fscache_begin_volume_access(9). slay, bye 💅✨