nilfs_mdt_get_block(9)

💜 nilfs_mdt_get_block(9) — from the Kernel API Manual, bestie ✨

okay so picture this: it's a kernel API manual page, the function is nilfs_mdt_get_block, and it lives in section 9 (that's the kernel-functions section, iykyk). she's a NILFS2 girlie and honestly? she ate. let's get into it 🎀

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🌸 NAME 🌸

nilfs_mdt_get_block — read or create a buffer on a meta data file, no cap 💅

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✨ SYNOPSIS ✨

int nilfs_mdt_get_block (struct inode *inode , unsigned long blkoff ,
       int create , void (*init_block)(struct inode *, struct buffer_head *,
       void *) , struct buffer_head **out_bh );

like, that's the whole signature, character for character, don't come for me 🫶

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🦋 ARGUMENTS 🦋

• inode — the inode of the meta data file. that's her main character energy right there 👑
• blkoff — block offset. literally just which block we're talking about.
• create — the create flag. non-zero means "yes bestie, make one if it's not there" ✨
• init_block — the initializer used for a newly allocated block. she does the formatting glow-up 💅
• out_bh — output of a pointer to the buffer_head. this is where the goods land 📦

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💖 DESCRIPTION 💖

so nilfs_mdt_get_block looks up the specified buffer, and it tries to create a new buffer if create is not zero. periodt.

and listen — if (and only if) this function succeeds, it stores a pointer to the retrieved buffer head in the location pointed to by out_bh. if and only if, bestie, that's not a vibe, that's a contract 🫡

the retrieved buffer may be either an existing one or a newly allocated one — either way she's serving 🍓

for a newly created buffer, if the callback function argument init_block is non-NULL, the callback will be called with the buffer locked to format the block. locked AND formatted, we love a responsible queen 🔒✨

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🔥 RETURN 🔥

0 on success 🌈 — or one of these negative error codes on failure, and yeah they're all giving sad girl hours 😭:

• -EIO — I/O error (including metadata corruption). the metadata is not okay 💀
• -ENOENT — the specified block does not exist (hole block). she's not there, she's on vacation 🕳️
• -ENOMEM — insufficient memory available. no thoughts, no RAM 🙈
• -EROFS — read only filesystem (for create mode). you cannot sit with us, it's read-only ⛔

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🧚 SEE ALSO 🧚

Kernel file ./fs/nilfs2/mdt.c, plus the whole friend group:

• nilfs_mdt_find_block(9)
• nilfs_mdt_delete_block(9)
• nilfs_mdt_forget_block(9)
• nilfs_mdt_clear(9)
• nilfs_mdt_destroy(9)
• nilfs_mdt_setup_shadow_map(9)
• nilfs_mdt_save_to_shadow_map(9)
• nilfs_mdt_restore_from_shadow_map(9)
• nilfs_mdt_clear_shadow_map(9)

the shadow map saga is real and honestly iconic 🌈👑

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ngl, if you're poking at a meta data file's buffers and you see -EIO staring back at you, check your metadata before you check your friends 💀

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okay that's the whole page, slay, go read the source bestie 💖

this lil masterpiece comes to you from ./fs/nilfs2, dated October 2026, and it is — say it with me — nilfs_mdt_get_block(9) 🎀✨🦋