Re: [PATCH] fuse: hold i_mutex in fuse_file_fallocate() - v2

From: Miklos Szeredi
Date: Mon Jun 17 2013 - 19:49:33 EST

On Thu, Jun 13, 2013 at 1:46 PM, Brian Foster <bfoster@xxxxxxxxxx> wrote:
> On 06/13/2013 04:16 AM, Maxim Patlasov wrote:
>> Changing size of a file on server and local update (fuse_write_update_size)
>> should be always protected by inode->i_mutex. Otherwise a race like this is
>> possible:
>> 1. Process 'A' calls fallocate(2) to extend file (~FALLOC_FL_KEEP_SIZE).
>> fuse_file_fallocate() sends FUSE_FALLOCATE request to the server.
>> 2. Process 'B' calls ftruncate(2) shrinking the file. fuse_do_setattr()
>> sends shrinking FUSE_SETATTR request to the server and updates local i_size
>> by i_size_write(inode, outarg.attr.size).
>> 3. Process 'A' resumes execution of fuse_file_fallocate() and calls
>> fuse_write_update_size(inode, offset + length). But 'offset + length' was
>> obsoleted by ftruncate from previous step.
>> Changed in v2 (thanks Brian and Anand for suggestions):
>> - made relation between mutex_lock() and fuse_set_nowrite(inode) more
>> explicit and clear.
>> - updated patch description to use ftruncate(2) in example
>> Signed-off-by: Maxim V. Patlasov <MPatlasov@xxxxxxxxxxxxx>

Thanks, applied.

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