Richard W.M. Jones wrote: > On Wed, Sep 03, 2008 at 12:36:55PM -0500, Eric Sandeen wrote: >> Hm, I probably need to get the fallocate.h header file included if it's >> not so that sys_fallocate can be used directly, but it is also exposed >> via posix_fallocate in glibc - tested here on xfs just because xfs_bmap >> is a handy way to show that it actually works via glibc: > > Uh, stupid me - I was looking for the wrong call. Rawhide _does_ have > it. > >>> (c) Does ext4 preallocate in the background? A synchronous >>> preallocate call isn't much use to virt-manager. >> It does not, but what is the concern? It doesn't take much time: > >> (on ext4 this time): >> >> [root@inode test]# time test_posix_fallocate testfile 0 10737418240 >> >> real 0m0.009s >> user 0m0.000s >> sys 0m0.009s > > OK ... I'm assuming though that the zeroes aren't all written to disk > in this time, so that is exactly what I wanted. No, zeros are never written to disk if the ->fallocate call is supported. They are allocated, but flagged on-disk as unwritten/uninitialized, so any read (before a write, of course) will return zeros without the need for all that pesky writing business.... -Eric -- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
