jbd2_journal_extend(9)

📦 version 7.3.1, in nixpkgs unstable

✨ jbd2_journal_extend(9) ✨

okay so this is a page from the Kernel API Manual (yes, the Kernel API Manual, we're fancy now 💅) and it's all about jbd2_journal_extend — the function that's basically the "bestie can I have a little more??" of the journaling world 🫶

🌸 NAME 🌸

jbd2_journal_extend — extend buffer credits. like literally just. more credits. 💖

🦋 SYNOPSIS 🦋

int jbd2_journal_extend (handle_t *handle , int nblocks , int
       revoke_records );

she takes three things and gives you back an int, no cap ✨

🎀 ARGUMENTS 🎀

  • handle — the handle you wanna 'extend'. that's the one, right there 👈
  • nblocks — nr blocks to try to extend by. try being the operative word here, we'll get to that 🙈
  • revoke_records — number of revoke records to try to extend by. also a try situation 💀

💜 DESCRIPTION 💜

so some transactions — think large extends and truncates — can be done atomically all at once, or in several stages. the operation requests a credit for a number of buffer modifications in advance, but it can extend its credit if it needs more. growth mindset fr fr 🌱

jbd2_journal_extend tries to give the running handle more buffer credits. key word: tries. it does not guarantee that allocation — this is a best-effort only situation, lowkey. and like, the calling process MUST be able to deal cleanly with a failure to extend here. no throwing a tantrum, no crashing, just handle it gracefully bestie 😭

⚠️ real talk: this is best-effort. if it fails, that's on you to deal with cleanly. the manpage is yelling MUST in all caps for a reason 👑

Return 0 on success, non-zero on failure.

and the vibes of those non-zero returns:

  • return code < 0 implies an error
  • return code > 0 implies normal transaction-full status

so like. negative = something went wrong 💀, positive = the transaction is just full, which is a whole normal thing, it's giving "we're at capacity, respectfully" 🌈

🔥 SEE ALSO 🔥

Kernel file ./fs/jbd2/transaction.c — and honestly the whole friend group:

like that's the entire group chat, go read all of them, iykyk 💅

and that's the page!! brought to you by ./fs/jbd2, dated October 2026, and yeah the title up top is jbd2_journal_extend(9) in case you forgot already 🎀 mwah, go extend some credits responsibly 🧚✨

📦 where this page comes from