nfs4_ff_layout_prepare_ds(9)

💅 nfs4_ff_layout_prepare_ds(9) 💅

ok so bestie, welcome to the Kernel API Manual ✨ — this is a kernel API page, and today's main character is nfs4_ff_layout_prepare_ds. it's giving flexfile layout energy, it's giving "get this DS connected before the RPC call", and honestly? we're obsessed. 🦋

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🌸 NAME 🌸

nfs4_ff_layout_prepare_ds — literally just prepare a DS connection for an RPC call. that's it, that's the vibe. 💖

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✨ SYNOPSIS ✨

struct nfs4_pnfs_ds * nfs4_ff_layout_prepare_ds (struct
pnfs_layout_segment *lseg , struct nfs4_ff_layout_mirror *mirror , u32
dss_id , bool fail_return );

like, copy it exactly bestie, don't @ me 🙈

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🎀 ARGUMENTS 🎀

• lseg — the layout segment we're operating on. yes, this one. the one we're doing stuff to. 🫶
• mirror — the layout mirror describing the DS to use. it's the mirror's whole moment, let it have it. ✨
• dss_id — the DS stripe id, used to select which stripe to use. pick your fighter, stripe edition. 💅
• fail_return — return layout on connect failure? a whole bool, a whole decision. 👑

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🔥 DESCRIPTION 🔥

so the goal here is: try to prepare a DS connection to accept an RPC call. no cap. that means selecting a mirror to use, and then connecting the client to it — but only if it's not already connected. if it's already connected, cool, we're not doing extra work for no reason. 💀

now, the way this works 😭 — since we only need a single functioning mirror to satisfy a read, we don't want to return the layout if there is one. one working mirror = read is fed, we're good, no dramatic exit needed. but for writes? completely different energy. for writes, any down mirror should result in a LAYOUTRETURN. like, every single one. no exceptions, periodt. 🚨

and fail_return is how we distinguish between the two cases — it's literally the ✨ flag that tells us which of those two situations we're in. iykyk. 🌈

on success it returns a pointer to a connected DS object. on failure it returns NULL. that's the whole return contract, love that for us. 💖

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🦋 SEE ALSO 🦋

• Kernel file ./fs/nfs/flexfilelayout/flexfilelayoutdev.c — go read it, bestie, it's right there 👀
• nfs4_ff_find_or_create_ds_client(9) — the friend we link up with 💜

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aaaand that's the page! 🎀 sign-off time: this lil masterpiece lives under ./fs/nfs/flexfilelayout, it's dated October 2026, and it's brought to you by nfs4_ff_layout_prepare_ds(9) — slay, bye! 💅✨🌸