file_write_started(9)

💅 file_write_started(9) — a whole Kernel API Manual moment

okay bestie, buckle up, because we're diving into the Kernel API Manual and today's main character is file_write_started(9). yes it's a real function. yes it's lowercase. yes she's iconic. 🌸

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✨ NAME ✨

file_write_started — literally just checks if SB_FREEZE_WRITE is held 🎀

🦋 SYNOPSIS 🦋

bool file_write_started (const struct file *file );

🌸 ARGUMENTS 🌸

• file — the file we write to. that's it. that's the whole argument. she's low maintenance 💅

💖 DESCRIPTION 💖

so here's the tea, bestie 👑

This can be a false positive with !CONFIG_LOCKDEP/LOCK_STATE_UNKNOWN. like, it might say "yeah write's started" when the vibe check is genuinely unknown. no cap.

It can also be a false positive with !S_ISREG, because file_start_write has no effect on !S_ISREG. so if it's not a regular file, the whole thing is basically doing nothing and our little check is out here guessing. 😭

fr fr, both of these are straight-up "may be false positive" situations — don't come for me, it's in the manual. 🫶

🔥 SEE ALSO 🔥

Kernel file ./include/linux/fs.h — and like, the entire extended fam 🧚:

• enum positive_aop_returns(9)
• struct address_space(9)
• struct file_ra_state(9)
• struct file(9)
• i_uid_into_vfsuid(9)
• i_uid_needs_update(9)
• i_uid_update(9)
• i_gid_into_vfsgid(9)
• i_gid_needs_update(9)
• i_gid_update(9)
• inode_fsuid_set(9)
• inode_fsgid_set(9)
• fsuidgid_has_mapping(9)
• inode_set_ctime(9)
• file_write_not_started(9)
• struct renamedata(9)
• is_mgtime(9)
• iput_if_not_last(9)
• is_idmapped_mnt(9)
• file_start_write(9)
• file_end_write(9)
• kiocb_start_write(9)
• kiocb_end_write(9)
• name_is_dot_dotdot(9)
• name_contains_dotdot(9)
• inode_dio_begin(9)
• inode_dio_end(9)
• generic_ci_validate_strict_name(9)

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and that's the whole page, bestie ✨ this one came straight out of ./include/linux and it's dated October 2026 — so yeah, she's from the future, and she ate. 💜 🎀 🍓