Re: sys_write() racy for multi-threaded append?

[Benjamin LaHaise]

> Actually, I think it would make the kernel (negligibly) faster to bump
> f_pos before the vfs_write() call.  Unless fget_light sets fput_needed
> or the write doesn't complete cleanly, you won't have to touch the
> file table entry again after vfs_write() returns.  You can adjust

Any number of things can cause a short write to occur, and rewinding the 
file position after the fact is just as bad.  A sane app has to either 
serialise the writes itself or use a thread safe API like pwrite().

		-ben
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