linux-kernel - Issue with Kexec memory allocation

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Message-ID: <CAFZWReakYoDcSgEXw-d-SPAzum=fw=uLo7sh8OMqZV6FjP1ymA@mail.gmail.com>
Date:   Mon, 6 Jan 2020 12:43:20 +0530
From:   Uday R <opensource.linuz@...il.com>
To:     linux-kernel@...r.kernel.org
Subject: Issue with Kexec memory allocation

Hello folks,

I am using kexec to load into the new kernel from the existing kernel.
My vmlinuz image size is 6.6MB, initrd size is 18MB, and the root file
system size is 715MB.  I use kexec command to load the new kernel into
memory. I observed that before calling kexec if the available memory
is less than 1.33GB then kexec lands into an out of memory issue
effectively kexec being killed by OOM-KILLER.  I dont get into out of
memory issue if i have memory >=1.33GB.

My question is why kexec tries to over allocate memory when the
available memory is less than 1.33GB and gets the available memory to
ZERO.
In case if the available memory is >= 1.33GB before calling kexec,
After kexec load, i see the memory consumed by kexec load is
approximately equal to size of "linux+initrd+root file system".

Is there a bug in the 'Kexec' code and had been fixed ?

Note: i am using the kernel from a vendor, Just wanted to know if
there is no such issue in mainstream code.

Thanks in Advance,
Uday