Messages in this thread | | | From | jiangyiwen <> | Subject | [V9fs-developer] [bug report] fs/9p: inode blocks show error in fscache mode | Date | Wed, 22 Nov 2017 17:31:06 +0800 |
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Hi all,
I test a scenario that will cause the difference of inode blocks between client and host, the scenario as follows:
Precondition: 1) use VirtFS(virtio-9p) to connect guest and host. 2) 9p dir in guest is /mnt/9p, host is /9p-host. 3) server fs is ext4 and block size is 4096.
Test steps: 1) on the client(guest) # touch /mnt/9p/test/file # dd if=/dev/zero of=/mnt/9p/test/file bs=1 count=1043456 seek=1302528 conv=notrunc
2) on the client(guest) # stat /mnt/9p/test/file the file's blocks is 4582 blocks(block size is 512)
3) on the server(host) # stat /9p-host/test/file the file's blocks is 2040 blocks(block size is 512)
Cause analysis: Because the file is sparse file, so in function v9fs_write_end will update inode blocks according to difference between last_pos and inode_size, only when last_pos is larger than the inode_size, then it update the blocks and inode_size, the operation is not fit the sparse file.
Currently I want to call v9fs_invalidate_inode_attr to invalidate inode, but it will influence the performance, so I don't have a good solution.
Please advise. Thanks in advance!
Best regards, Yiwen
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