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Diffstat (limited to 'Documentation/power/swsusp-and-swap-files.txt')
| -rw-r--r-- | Documentation/power/swsusp-and-swap-files.txt | 60 |
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diff --git a/Documentation/power/swsusp-and-swap-files.txt b/Documentation/power/swsusp-and-swap-files.txt deleted file mode 100644 index f281886de490..000000000000 --- a/Documentation/power/swsusp-and-swap-files.txt +++ /dev/null @@ -1,60 +0,0 @@ -Using swap files with software suspend (swsusp) - (C) 2006 Rafael J. Wysocki <rjw@sisk.pl> - -The Linux kernel handles swap files almost in the same way as it handles swap -partitions and there are only two differences between these two types of swap -areas: -(1) swap files need not be contiguous, -(2) the header of a swap file is not in the first block of the partition that -holds it. From the swsusp's point of view (1) is not a problem, because it is -already taken care of by the swap-handling code, but (2) has to be taken into -consideration. - -In principle the location of a swap file's header may be determined with the -help of appropriate filesystem driver. Unfortunately, however, it requires the -filesystem holding the swap file to be mounted, and if this filesystem is -journaled, it cannot be mounted during resume from disk. For this reason to -identify a swap file swsusp uses the name of the partition that holds the file -and the offset from the beginning of the partition at which the swap file's -header is located. For convenience, this offset is expressed in <PAGE_SIZE> -units. - -In order to use a swap file with swsusp, you need to: - -1) Create the swap file and make it active, eg. - -# dd if=/dev/zero of=<swap_file_path> bs=1024 count=<swap_file_size_in_k> -# mkswap <swap_file_path> -# swapon <swap_file_path> - -2) Use an application that will bmap the swap file with the help of the -FIBMAP ioctl and determine the location of the file's swap header, as the -offset, in <PAGE_SIZE> units, from the beginning of the partition which -holds the swap file. - -3) Add the following parameters to the kernel command line: - -resume=<swap_file_partition> resume_offset=<swap_file_offset> - -where <swap_file_partition> is the partition on which the swap file is located -and <swap_file_offset> is the offset of the swap header determined by the -application in 2) (of course, this step may be carried out automatically -by the same application that determines the swap file's header offset using the -FIBMAP ioctl) - -OR - -Use a userland suspend application that will set the partition and offset -with the help of the SNAPSHOT_SET_SWAP_AREA ioctl described in -Documentation/power/userland-swsusp.txt (this is the only method to suspend -to a swap file allowing the resume to be initiated from an initrd or initramfs -image). - -Now, swsusp will use the swap file in the same way in which it would use a swap -partition. In particular, the swap file has to be active (ie. be present in -/proc/swaps) so that it can be used for suspending. - -Note that if the swap file used for suspending is deleted and recreated, -the location of its header need not be the same as before. Thus every time -this happens the value of the "resume_offset=" kernel command line parameter -has to be updated. |