crypt_extent(9)

💅 crypt_extent(9) — Kernel API Manual 🎀

okay so this is crypt_extent(9) from the Kernel API Manual, and bestie, we're about to get into some eCryptfs crypto business. buckle up ✨

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🌸 NAME 🌸

crypt_extent —

and that's it. that's the whole name section. the description after the dash is literally blank, no cap, nothing there. the dash is just standing there alone with main character energy 💀 iconic of it honestly.

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🦋 SYNOPSIS 🦋

int crypt_extent (struct ecryptfs_crypt_stat *crypt_stat , struct page
*dst_page , struct page *src_page , pgoff_t page_index , unsigned long
extent_offset , int op );

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✨ ARGUMENTS ✨

• crypt_stat — the crypt_stat holding the cryptographic context for the encryption operation. it's giving "everything you need to know lives in here" 🫶
• dst_page — the page you write the result into. the destination, the landing spot, the final boss 🎯
• src_page — the page you read from. the source, the origin story 🌱
• page_index — the offset in the file, in units of PAGE_SIZE (yes, in units of PAGE_SIZE, not bytes, don't come for me)
• extent_offset — the page extent offset, used when generating the IV. lowkey crucial 🔥
• op — ENCRYPT or DECRYPT, telling us which operation we actually want. pick one, bestie 💅

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🌈 DESCRIPTION 🌈

so what does it actually do? it encrypts or decrypts one extent of data. that's the whole vibe. one extent, in or out, done 🧚

and it returns zero on success; non-zero otherwise. classic Unix behavior — zero is the happy ending, anything else means something went sideways 😭

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👑 SEE ALSO 👑

Kernel file ./fs/ecryptfs/crypto.c, plus this absolutely stacked friend group of man pages (like, the whole ecryptfs extended universe fr fr):

• ecryptfs_from_hex(9)
• ecryptfs_derive_iv(9)
• ecryptfs_init_crypt_stat(9)
• ecryptfs_destroy_crypt_stat(9)
• virt_to_scatterlist(9)
• crypt_scatterlist(9)
• ecryptfs_encrypt_page(9)
• ecryptfs_decrypt_page(9)
• ecryptfs_init_crypt_ctx(9)
• ecryptfs_copy_mount_wide_flags_to_inode_flags(9)
• ecryptfs_set_default_crypt_stat_vals(9)
• ecryptfs_new_file_context(9)
• ecryptfs_validate_marker(9)
• ecryptfs_process_flags(9)
• write_ecryptfs_marker(9)
• ecryptfs_code_for_cipher_string(9)
• ecryptfs_cipher_code_to_string(9)
• ecryptfs_write_headers_virt(9)
• ecryptfs_write_metadata(9)
• set_default_header_data(9)
• ecryptfs_read_headers_virt(9)
• ecryptfs_read_xattr_region(9)
• ecryptfs_process_key_cipher(9)
• ecryptfs_destroy_crypto(9)
• ecryptfs_tfm_exists(9)
• ecryptfs_get_tfm_and_mutex_for_cipher_name(9)
• ecryptfs_encode_for_filename(9)
• ecryptfs_decode_from_filename(9)
• ecryptfs_encrypt_and_encode_filename(9)
• ecryptfs_decode_and_decrypt_filename(9)

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that's the whole page, bestie, you ate that 💖 this one shipped out of ./fs/ecryptfs back in October 2026 — shoutout to the source and the date, mwah, go read the other thirty man pages now 🍓✨