readahead_expand(9)

💖 readahead_expand(9) 💖

okay bestie, welcome to the Kernel API Manual — today’s main character is readahead_expand, and she is here to make a readahead request bigger. no cap. 🫶

🌸 NAME 🌸

readahead_expand — expand a readahead request ✨

🦋 SYNOPSIS 🦋

       void readahead_expand (struct readahead_control *ractl , loff_t
       new_start , size_t new_len );

✨ ARGUMENTS ✨

• ractl — the request to be expanded, she’s the one getting the glow-up 💅
• new_start — the revised start
• new_len — the revised size of the request

💫 DESCRIPTION 💫

so here’s the vibe: this function attempts to expand a readahead request outwards from the current size to the specified size, by inserting locked pages before and after the current window so the size increases to the new window. 🌈

this may involve the insertion of THPs, in which case the window may get expanded even beyond what was requested. yes, bestie, it can overshoot — it’s giving “we went a little extra” 😭

the algorithm will stop if it encounters a conflicting page already in the pagecache and leave a smaller expansion than requested. lowkey tragic, but that’s the rule 💀

the caller must check for this by examining the revised ractl object for a different expansion than was requested. literally check your revised ractl, bestie — the expansion might not be the one you asked for 👑

🌟 SEE ALSO 🌟

• Kernel file ./mm/readahead.c — Readahead Overview(9)
• read_pages(9)
• page_cache_ra_unbounded(9)

mwah 💋 this page is signed off from ./mm, October 2026 edition — readahead_expand(9) out. stay hydrated and may your expansions be exactly what you requested (unless THPs say otherwise) 🎀💖