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s2disk/s2both may fail unnecessarily and erratically if NR_FILE_MAPPED is high - for instance when using VMs with VirtualBox and perhaps VMware Player. In those situations s2disk becomes unreliable and therefore unusable. A typical scenario is: user issues a s2disk and it fails. User issues a second s2disk immediately after that and it succeeds. And user wonders why. The problem is caused by minimum_image_size() in snapshot.c. The value it returns is roughly 100% too high because NR_FILE_MAPPED is subtracted in its calculation. Eventually the number of preallocated image pages is falsely too low. This doesn't matter as long as NR_FILE_MAPPED-values are in a normal range or in 32bit-environments as the code allows for allocation of additional pages from highmem. But with the high values generated by VirtualBox-VMs (a 2-GB-VM causes NR_FILE_MAPPED go up by 2 GB) it may lead to failure in 64bit-systems. Not subtracting NR_FILE_MAPPED in minimum_image_size() solves the problem. I've done at least hundreds of successful s2both/s2disk now on an x86_64 system (with and without VirtualBox) which gives me some confidence that this is right. It has turned s2disk/s2both from unusable into 100% reliable. Link: https://bugzilla.kernel.org/show_bug.cgi?id=97201 Signed-off-by: Rainer Fiebig <jrf@mailbox.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.