jffs2_reserve_space(9)

💅 jffs2_reserve_space(9) — like, the Kernel API Manual entry, bestie ✨

okay so picture this: you're deep in the kernel, you're in jffs2, and you need actual physical room on the flash to write your nodes. that's this function. this is the girl who gets you the space. she's from the Kernel API Manual and she does not miss 🎀

---

🌸 NAME 🌸

jffs2_reserve_space — request physical space to write nodes to flash

like, she literally books the venue for your nodes. iconic behavior only.

---

✨ SYNOPSIS ✨

int jffs2_reserve_space (struct jffs2_sb_info *c , uint32_t minsize ,
uint32_t *len , int prio , uint32_t sumsize );

look at her. five arguments. she's high maintenance but she's worth it 💖

---

🦋 ARGUMENTS 🦋

• c — superblock info 💫 (the context, the situation, the ~lore~)
• minsize — the minimum acceptable size of the allocation. like, she will not go below this, do not even ask
• len — the returned value of the allocation length. it's the output, she fills it in for you, bestie 🫶
• prio — the allocation type, and it's one of ALLOC_{NORMAL,DELETION} 🔥
• sumsize — the summary size requested, or JFFS2_SUMMARY_NOSUM_SIZE if you want no summary at all 🙈

---

👑 DESCRIPTION 👑

okay so what she does: she requests a block of physical space on the flash. that's the whole vibe. she goes and gets you room. mm-hmm. 💅

here's the part you can't skip, bestie, like genuinely the most important part:

if it returns 0, jffs2_reserve_space also downs the per-filesystem allocation semaphore — that's so that no more than one allocation can be active at any single time, periodt. that semaphore gets released later by jffs2_commit_allocation. so like, don't forget to commit, because she is holding that lock and she will hold it 💀

and she may trigger garbage collection in order to make room for the requested allocation. yes, she'll literally take out the trash to get you your space. main character energy fr fr 🌈

---

⭐ RETURN ⭐

• 0 for success, and she puts 'len' into the appropriate place 🎉
• or it returns -ENOSPC or another error if appropriate 😭

and note this cutie detail: it doesn't return len since that's already returned in len. she said why would I say it twice. no cap. 🙈

---

🍓 SEE ALSO 🍓

• Kernel file ./fs/jffs2/nodemgmt.c
• jffs2_add_physical_node_ref(9)

---

⚠️ real talk: that semaphore thing is not a suggestion. if you get a 0 back, the per-filesystem allocation semaphore is downed and it's on you to release it with jffs2_commit_allocation. don't leave her hanging 🫶

---

and that's the page, bestie 🧚 source is ./fs/jffs2, dated October 2026, and the whole thing is filed under jffs2_reserve_space(9) — mwah, slay, go write some nodes to flash 💜🎀