VOP_STRATEGY(9)

💅 VOP_STRATEGY — the "read or write a file system buffer" page (yes bestie, it's a section 9 kernel dev manual, come thru)

okay so. if you're poking at the guts of a kernel, VOP_STRATEGY(9) is the lil' vnode operation that does the actual I/O for a file system buffer. she reads, she writes, she blocks. main character energy, no cap. 🎀

✨ SYNOPSIS ✨

#include <sys/param.h>
#include <sys/vnode.h>

int
VOP_STRATEGY(struct vnode *vp, struct buf *bp);

like literally just two headers and one function, we love a minimal slay 💖

🌸 DESCRIPTION 🌸

so here's the tea on the arguments:

• vp — the vnode that the buffer is for. it's giving "whose buffer is this" energy 🦋
• bp — the buffer that's getting read or written. the moment of truth.

this call either reads or writes data from a file, and which one it does depends entirely on the value of bp->b_io.bio_cmd. so like, check that field, bestie, it's the vibe check of the whole operation 🔥

the call may block. so don't be out here acting surprised when it does. she's allowed to take her time. periodt.

💫 RETURN VALUES 💫

okay so this is the part where it gets a little unhinged: this function always returns zero. zero. always. 0. every single time. 🤡

so how do errors get reported?? not via the return value, that's for sure. if something goes wrong you have to:

• set BIO_ERROR on the b_ioflags field in struct buf, and
• set b_error to the appropriate errno value.

that's the whole entire protocol. set the flag, set the errno, return 0, go about your day. iconic behaviour honestly 💅

👑 SEE ALSO 👑

• buf(9)
• vnode(9)

go read those too, iykyk 📚

🫶 AUTHORS 🫶

this manual page was written by Doug Rabson. thank u doug, we love u, ur doing amazing sweetie 💜

and that's the whole page, bestie!! this one comes to you from the Debian crew, dated February 2, 2014 — an absolute classic, a real vintage moment, and she still hits. now go read buf(9) like i told you. mwah 🌈💖✨