Messages in this thread | | | From | Manfred Spraul <> | Subject | Re: 2.3.7: generic_write_page(): O_APPEND & inode->i_size not SMP safe | Date | Tue, 22 Jun 1999 12:46:39 +0200 (CST) |
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I cc'ed Alexander, because I think this is mostly a VFS SMP problem.
Ingo wrote: > > >2) setting inode->i_size is not SMP safe. > > Your fix looks good I'm not sure: think about 2 processes with O_APPEND: they still write to the same address, if this is a log file, then 1 log record will be lost.
> note that Alexander Viro is > working on SMP-threading the VFS, which will change those places that > update filep fields.]
I think that the file pointer and the actual write operation must be coherent (i.e. if two threads write data with the same filp, then they must write to different addresses; and if a write operation is aborted in the middle, then we must handle that gracefully [no data leak with uninitialized memory, can we advance the file pointer even if the data bytes were never written?]).
Note that with O_APPEND, inode->i_size replaces the file pointer for write operation, so cannot implement a lazy inode->i_size update (i.e. writing and updating i_size when we obtain the kernel lock).
I'll wait for the patch from Alexander. -- Manfred
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