Hi, Amit Uttamchandani wrote:
Hello,I understand that fuse has implemented fallocate support. I have obtained the latest sources of ntfs-3g from git and noticed this is not implemented yet. Are there any plans to support this? In the meantime, I tried to simulate an fallocate by using ntfscp code and instead of doing copy just create the file, change the size using ntfs_attr_truncate_solid(). Then, I close the attr, inode, and unmount the volume. The file gets created with the correct size (4GB). However, this is not reflected in the filesystem. Checking the free space, shows the same amount of free space as before the 4GB file creation. Am I missing a step here?
This is a bug in ntfs_attr_truncate_solid() leading to a sparse file instead of a file whose space is fully allocated, which occurs when the data is resident initially. You can avoid the bug by writing 4K bytes before calling ntfs_attr_truncate_solid(). Attached is a patch to fix the bug. With this procedure you will allocate disk space without writing to the allocated space. However data previously written to the same space can be read, so providing a fallocate() on a similar base is not acceptable. You will get a better result by issuing a command such as dd if=/dev/zero of=allocated_file bs=65536 count=65536 Now, NTFS has a limited possibility to allocate space to a file without writing to it, still making the space appearing as zeroed. The probable consequence would be that only sequential writing from the beginning of the file would be allowed. I have not examined further. Can you explain why you want to allocate space without writing to that space, and how you would use the allocated space ? Regards Jean-Pierre
allocate.patch.gz
Description: GNU Zip compressed data
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