From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: md disk fault communication code
Date: Fri, 18 Apr 2014 16:13:34 +1000
Message-ID: <20140418161334.025262bb@notabene.brown>
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To: Sonu a <p10sonu@gmail.com>
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On Fri, 18 Apr 2014 13:38:58 +0800 Sonu a <p10sonu@gmail.com> wrote:

> when disk is removed with out mdadm as I see from the stack below the
> communication reaching the md driver.
>=20
> dump_stack+0x49/0x5e
> md_error+0x50/0x110 [md_mod]
> state_store+0x43/0x300 [md_mod]
> rdev_attr_store+0xad/0xd0 [md_mod]
> ? sysfs_write_file+0x62/0x1c0
> sysfs_write_file+0x138/0x1c0
> vfs_write+0xc0/0x1e0
> SyS_write+0x5a/0xa0
> ? __audit_syscall_exit+0x246/0x2f0
> system_call_fastpath+0x16/0x1b
>=20
> could someone point me to the code which is monitoring scsi disks
> status and thus calling md driver sysfs interface accordingly ?

I think you ask asking how md_error gets called when a SCSI device fails,
having already discovered how it is called when you explicitly write to a
sysfs file.

Nothing monitors the scsi disks.  md only discovers failure if it sends a
request to a disk, and the request signals an error.  If you search for
'bi_end_io', functions assigned to this field are called when a request
finishes.  Those functions might call md_error if the request failed, or th=
ey
might schedule some other handling first to try to correct the error.

NeilBrown

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