xdr_buf_to_sg_alloc(9)

🌸 NAME 🌸

okay bestie, meet xdr_buf_to_sg_alloc — the function that populates a scatterlist for an xdr_buf range. This is the xdr_buf_to_sg_alloc(9) page from the Kernel API Manual, and yes, we’re gonna get through it together 💖

✨ SYNOPSIS ✨

int xdr_buf_to_sg_alloc (const struct xdr_buf *buf , unsigned int offset
, unsigned int len , struct scatterlist *sg_head , unsigned int
sg_head_nents , struct scatterlist **sg_overflow , gfp_t gfp );

🫶 ARGUMENTS 🫶

• buf — the xdr_buf to map. literally the thing you’re mapping, bestie 🦋
• offset — starting byte offset within buf.
• len — number of bytes to cover.
• sg_head — caller-provided scatterlist array (typically stack-allocated). yes, you bring the array, iconic of you 🎀
• sg_head_nents — number of entries in sg_head.
• sg_overflow — OUT: chained extension, or NULL when sg_head sufficed.
• gfp — memory allocation flags for overflow.

💅 DESCRIPTION 💅

When the xdr_buf fits, it populates sg_head directly. When more entries are needed, an overflow scatterlist is allocated and chained from sg_head so that the result is traversable with sg_next. that’s the whole vibe: direct fill if it fits, chained overflow if it doesn’t 💅

👑 RETURN 👑

On success, the return value is the number of populated scatterlist entries (counting only data entries, not chain entries). sg_head is the head of the resulting list. Caller must kfree sg_overflow when done. On failure, a negative errno. do not forget the kfree, bestie, I’m serious 😭

🦋 SEE ALSO 🦋

Kernel file ./net/sunrpc/xdr.c — and the whole squad:

• xdr_encode_opaque_fixed(9)
• xdr_encode_opaque(9)
• xdr_terminate_string(9)
• xdr_buf_to_bvec(9)
• xdr_buf_to_sg(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_reserve_space_vec(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)

This gem is from ./net/sunrpc, dated October 2026, and it’s literally xdr_buf_to_sg_alloc(9) — mwah, go slay your scatterlist 💋✨