fs: Add FITRIM ioctl
Adds an filesystem independent ioctl to allow implementation of file system batched discard support. I takes fstrim_range structure as an argument. fstrim_range is definec in the include/fs.h and its definition is as follows. struct fstrim_range { start; len; minlen; } start - first Byte to trim len - number of Bytes to trim from start minlen - minimum extent length to trim, free extents shorter than this number of Bytes will be ignored. This will be rounded up to fs block size. It is also possible to specify NULL as an argument. In this case the arguments will set itself as follows: start = 0; len = ULLONG_MAX; minlen = 0; So it will trim the whole file system at one run. After the FITRIM is done, the number of actually discarded Bytes is stored in fstrim_range.len to give the user better insight on how much storage space has been really released for wear-leveling. Signed-off-by: NLukas Czerner <lczerner@redhat.com> Reviewed-by: NDmitry Monakhov <dmonakhov@openvz.org> Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
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