xdr_reserve_space_vec(9)

💅 xdr_reserve_space_vec(9) — from the Kernel API Manual

okay so bestie, buckle up, we're doing kernel XDR today ✨ this one lives in the 9 section of the kernel API manual and it's genuinely so straightforward you'll be obsessed 🫶

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✨ NAME ✨

xdr_reserve_space_vec — reserves a large amount of buffer space for sending 💖

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🎀 SYNOPSIS 🎀

int xdr_reserve_space_vec (struct xdr_stream *xdr , size_t nbytes );

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🌸 ARGUMENTS 🌸

• xdr — pointer to xdr_stream (the stream bestie in question 💅)
• nbytes — number of bytes to reserve

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🦋 DESCRIPTION 🦋

so here's the vibe 🌈 the size argument that gets passed to xdr_reserve_space is determined based on the number of bytes remaining in the current page — and the whole reason for that is to avoid invalidating iov_base pointers when xdr_commit_encode is called. no cap, that's the entire point of this little guy 💀

Return values, fr fr:

• 0 — success, slay 👑
• -EMSGSIZE — not enough space is available in xdr 😭

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⭐ SEE ALSO ⭐

Kernel file ./net/sunrpc/xdr.c — plus the whole ensemble cast, and yes I'm listing every single one because they all ate 🔥

• xdr_encode_opaque_fixed(9)
• xdr_encode_opaque(9)
• xdr_terminate_string(9)
• xdr_buf_to_bvec(9)
• xdr_buf_to_sg(9)
• xdr_buf_to_sg_alloc(9)
• xdr_inline_pages(9)
• _shift_data_left_pages(9)
• _shift_data_right_pages(9)
• _copy_to_pages(9)
• _copy_from_pages(9)
• xdr_buf_pages_zero(9)
• xdr_shrink_bufhead(9)
• xdr_shrink_pagelen(9)
• xdr_stream_pos(9)
• xdr_page_pos(9)
• xdr_init_encode(9)
• xdr_init_encode_pages(9)
• __xdr_commit_encode(9)
• xdr_reserve_space(9)
• xdr_truncate_encode(9)
• xdr_truncate_decode(9)
• xdr_restrict_buflen(9)
• xdr_write_pages(9)
• xdr_init_decode(9)
• xdr_init_decode_pages(9)
• xdr_finish_decode(9)
• xdr_inline_decode(9)
• xdr_read_pages(9)
• xdr_set_pagelen(9)
• xdr_enter_page(9)
• xdr_buf_subsegment(9)
• xdr_stream_subsegment(9)
• xdr_stream_move_subsegment(9)
• xdr_stream_zero(9)
• xdr_buf_trim(9)
• xdr_stream_decode_string_dup(9)
• xdr_stream_decode_opaque_auth(9)
• xdr_stream_encode_opaque_auth(9)

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💜 reminder bestie: -EMSGSIZE isn't a moral failure, it just means the xdr buffer literally had no room. check your space before you go reserving, iykyk 🙈

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anyway, that's the whole page 🧚 this cutie is from ./net/sunrpc, dated October 2026 — go forth and reserve responsibly, periodt 💅🍓