PROBE::IOBLOCK_TRACE.REQUEST(3stap)

💖 PROBE::IOBLOCK_TRACE.REQUEST 💖

okay bestie, gather round, because this is a page from the SystemTap Tapset Reference and it's literally the moment a block I/O request is born. no cap. it's a 3stap manual, so you know it's tapset business 💅

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✨ NAME ✨

probe::ioblock_trace.request — fires just as a generic block I/O request is created for a bio. like, the very instant. the origin story. the main character entrance 🎬✨

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🎀 SYNOPSIS 🎀

probe ioblock_trace.request {}

that's it. that's the whole vibe. no args, no drama, just a probe point sitting there waiting for bios 🦋

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🌸 VALUES 🌸

these are all the little goodies you can peek at inside the probe. every single one, no skipping, we're doing the full tour 🫶

• size — total size in bytes, the whole shebang 📏
• p_start_sect — points to the start sector of the partition structure of the device 🧭
• q — the request queue on which this bio was queued. yes queen, get in line 👑
• vcnt — bio vector count, which represents the number of array elements (page, offset, length) that make up this I/O request 🧮
• ino — i-node number of the mapped file 📁
• bytes_done — number of bytes transferred ✅
• name — name of the probe point 🏷️
• rw — binary trace for read/write request 📖✍️
• flags — see below, it's a whole mood board of bio states:
  • BIO_UPTODATE 0 — ok after I/O completion ✨
  • BIO_RW_BLOCK 1 — RW_AHEAD set, and read/write would block 🛑
  • BIO_EOF 2 — out-out-bounds error 😭
  • BIO_SEG_VALID 3 — nr_hw_seg valid 👍
  • BIO_CLONED 4 — doesn't own data 👯
  • BIO_BOUNCED 5 — bio is a bounce bio 🏀
  • BIO_USER_MAPPED 6 — contains user pages 🧑
  • BIO_EOPNOTSUPP 7 — not supported 🙅
• bdev_contains — points to the device object which contains the partition (when the bio structure represents a partition) 🗂️
• sector — beginning sector for the entire bio 🎯
• idx — offset into the bio vector array phys_segments - number of segments in this bio after physical address coalescing is performed 🔗
• devname — block device name 💾
• opf — operations and flags 🎛️
• bdev — target block device 🎯

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🌈 CONTEXT 🌈

the process makes block I/O request. periodt. that's the context, bestie 🫡

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💜 SEE ALSO 💜

• tapset::ioblock(3stap) — go read the whole ioblock tapset family, iykyk 📚

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ngl, if you're tracing block I/O and you skipped this probe, that's a red flag 🚩 it fires just as the request gets created, so it's giving "front row seats to the whole story" energy 🔥

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mwah 💋 this was brought to you by the SystemTap Tapset Reference, September 2026 edition — go forth and trace, you absolute icon 👑💖✨