ubifs_compress_folio(9)

💅 ubifs_compress_folio (Kernel API Manual, bestie) 💅

Okay so real talk, this one is from the Kernel API Manual and it's genuinely so useful once it clicks. Strap in 🎀

✨ NAME ✨

ubifs_compress_folio — compress folio. That's the whole vibe. It compresses a folio, no cap. 🦋

🌸 SYNOPSIS 🌸

void ubifs_compress_folio (const struct ubifs_info *c , struct folio
*in_folio , size_t in_offset , int in_len , void *out_buf , int *out_len
, int *compr_type );

Yes it returns void, yes there are seven arguments, and yes we're gonna go through every single one of them because that's just who I am 💅

🧚 ARGUMENTS 🧚

• c — the UBIFS file-system description object. Your whole filesystem's little identity card, basically 👑
• in_folio — the data to compress. The main character of this function, fr 🫶
• in_offset — offset into in_folio. Like, where in the folio we actually start looking.
• in_len — length of the data to compress. How much of it we're grabbing.
• out_buf — output buffer where the compressed data should be stored. The destination, the moment, the slay ✨
• out_len — output buffer length is returned here. So you hand it a pointer and it writes the length back. It's giving "I'll tell you how big it ended up being" 😌
• compr_type — type of compression to use on enter, and the actually used compression type on exit. Lowkey a two-way street, it reads it on the way in and rewrites it on the way out 🔥

💖 DESCRIPTION 💖

So what does it do? It compresses the input folio in_folio of length in_len, and it stores the result in the output buffer out_buf plus the resulting length in out_len. Iconic behavior, truly. 🎀

But here's the part everyone forgets: if the input buffer does not compress, it's just copied to out_buf. No drama, no error, it just gets yeeted straight through as-is. And the exact same thing happens if compr_type is UBIFS_COMPR_NONE — or if a compression error occurred. So like, three different roads, all leading to "fine, we copy it then" 💀

Note, and this is the important bit bestie: if the input buffer was not compressed, it is copied to the output buffer and UBIFS_COMPR_NONE is returned in compr_type. So always check compr_type after, iykyk 👀

🌈 SEE ALSO 🌈

Kernel file ./fs/ubifs/compress.c, plus the whole friend group:

• ubifs_compress(9)
• ubifs_decompress(9)
• ubifs_decompress_folio(9)
• compr_init(9)
• compr_exit(9)
• ubifs_compressors_init(9)
• ubifs_compressors_exit(9)

And that's the page! 🍓 Huge thanks to ./fs/ubifs for existing, dated October 2026, and to this manual page itself for being ubifs_compress_folio(9) — go compress something, bestie, you got this 💜✨