IOCTL-XFS-H...MONITORED-FS(2)

💖 ioctl_xfs_health_fd_on_monitored_fs — bestie check 💖

okay so real talk, this is a page from the System Calls Manual (section 2, the syscall girlies), and it's all about one specific XFS ioctl. come sit with me 🫶

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✨ NAME ✨

ioctl_xfs_health_fd_on_monitored_fs — the lil function that checks whether the fd you're holding actually belongs to the same filesystem that's being monitored 👀

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🌸 SYNOPSIS 🌸

#include <xfs/xfs_fs.h>

int ioctl(int healthmon_fd, XFS_IOC_HEALTH_FD_ON_MONITORED_FS, struct
xfs_health_file_on_monitored_fs *arg);

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🦋 DESCRIPTION 🦋

so this is an XFS healthmon fd ioctl, and what it does is literally just ask the kernel driver: "hey bestie, does the file descriptor we passed in through arg point to a file that lives on the same filesystem that healthmon_fd is monitoring?" 💅

and the fd gets conveyed in a struct that looks exactly like this, no notes:

struct xfs_health_file_on_monitored_fs {
     __s32 fd;
     __u32 flags;
};

• the flags field must be zero. like, zero zero. not negotiable 🚫
• the fd field is a descriptor of an open file 📂

and one more thing — healthmon_fd must be a file that was opened via the XFS_IOC_HEALTH_MONITOR ioctl. that's the vibe check it has to pass. no cap.

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⭐ RETURN VALUE ⭐

if something goes wrong, -1 gets returned and errno is set to tell you what happened 😭

but if the file descriptor does point to a file on the same filesystem that's being monitored? you get 0 back. slay. ✨

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💀 ERRORS 💀

error codes can be one of these, but lowkey not limited to just these:

• ESTALE — the open file is not on the same filesystem that's being monitored. different fs, different vibe, not it 🙈
• EINVAL — one or more of the arguments you specified is invalid. check ur inputs bestie.
• EBADF — arg.fd does not refer to an open file. it's giving closed, and not in the cute way 💔
• EFAULT — the arg structure could not be copied into the kernel. the copy failed, periodt.
• ENOTTY — healthmon_fd is not an XFS health monitoring file. wrong file, wrong energy 😤

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👑 CONFORMING TO 👑

this API is specific to the XFS filesystem on the Linux kernel. iykyk 🐧

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🌈 SEE ALSO 🌈

• ioctl_xfs_health_monitor(2)

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and that's the whole page, bestie, you ate it 💅✨ written by the XFS girlies, dated 2026-01-04, and yeah — that's the manual, section 2, no cap, we're done here. mwah 🎀🫶💖