fscrypt_setup_filename(9)

💖 fscrypt_setup_filename(9) 💖

okay so this is a page from the Kernel API Manual, bestie — it's fscrypt_setup_filename(9) and it's literally about getting your filename ready before you go poking around in a directory that might be encrypted. lowkey iconic kernel internals. let's get into it 🫶

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✨ NAME ✨

fscrypt_setup_filename — prepare to search a possibly encrypted directory

like, you're about to look something up in a dir and it might be encrypted, so you gotta prep first. that's the whole vibe check 🔥

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🌸 SYNOPSIS 🌸

int fscrypt_setup_filename (struct inode *dir , const struct qstr *iname
, int lookup , struct fscrypt_name *fname );

that's the signature, no cap. copy it exactly, don't be out here "fixing" the spacing 💅

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🦋 ARGUMENTS 🦋

• dir — the directory that will be searched. the scene of the crime 🎀
• iname — the user-provided filename being searched for. like, the name the user typed, fr fr.
• lookup — this one's a lil boolean-ish situation, so listen up:
  • 1 if we're allowed to proceed without the key, because it's ->lookup or we're finding the dir_entry for deletion;
  • 0 if we cannot proceed without the key, because we're going to create the dir_entry.
• fname — the filename information to be filled in. it's the output struct, she gets decorated ✨

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💜 DESCRIPTION 💜

okay so here's the tea. given a user-provided filename iname, this function sets fname->disk_name to the name that would be stored in the on-disk directory entry — if possible. not me being all "if possible" about it 😭

if the directory is unencrypted, this is simply iname. easy. no encryption arc, we move on.

else — if we have the directory's encryption key — then iname is the plaintext, so we encrypt it to get the disk_name.

else, for keyless lookup operations, iname should be a no-key name, so we decode it to get the struct fscrypt_nokey_name. and bestie, non-lookup operations will be impossible in this case, so we fail them with ENOKEY. that's not me being dramatic, that's literally what it says 💀

🌟 if it's successful, fscrypt_free_filename must be called later to clean up. don't forget. she's your responsibility now. clean up after yourself, periodt.

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⭐ RETURN ⭐

• 0 on success 🎉
• -errno on failure 🙈

that's it. that's the return. very demure, very mindful.

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🌈 SEE ALSO 🌈

all the siblings in the fscrypt filename cinematic universe, go check them out 👑

• Kernel file ./fs/crypto/fname.c
• fscrypt_fname_encrypt(9)
• fname_decrypt(9)
• fscrypt_fname_encrypted_size(9)
• fscrypt_fname_alloc_buffer(9)
• fscrypt_fname_free_buffer(9)
• fscrypt_fname_disk_to_usr(9)
• fscrypt_match_name(9)
• fscrypt_fname_siphash(9)

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🎀 and that's the whole page, bestie! this one lives in ./fs/crypto, dated October 2026 — so like, future vibes only. stay encrypted, stay slay 💖✨💅