Hallo Matthew:
[...] If the user does set their own "wsize", any value that is not a multiple of PAGE_SIZE is dangerous right? Shouldn't we prevent the user from corrupting their data (un)intentionally if they happen to specify a wrong value?
I already pointed that out in my e-mail dated 07.02.24 together with other potential issues: https://www.spinics.net/lists/linux-cifs/msg30973.html I'll recap here: 1) If the user specifies a wsize which is not multiple of PAGE_SIZE, I would abort, instead of issuing a warning. Like you said, it's too risky, you will corrupt data and you may not see the warning in an automated environment where connections are scripted. 2) Whether error or warning, I would state in the message that this is a temporary limitation. This "fix", which is more of a work-around, will probably be used for years, and people are going to think that the multiple of PAGE_SIZE is a permanent limitation in the client or the SMB protocol, which is not the case. 3) I am worried that, if the server states 60 KiB, and the CIFS client rounds it up to 64 KiB, then the connection will no longer work, because the CIFS client is exceeding the maximum that the server stated. I wouldn't warn, I would just abort the connection in this case too. With an old Windows Server and a page size of 64 KiB (like some ARM architecture already has), it is no longer an unlikely scenario, it will certainly occur. In my case, the connection negotiated a wsize of 16580, even though the server should actually default to 16644 bytes(?). In any case, well below 64 KiB. Now that I mentioned misleading messages: The man page for mount.cifs, parameters rsize and wsize, talks about "maximum amount of data the kernel will request", and about the "maximum size that servers will accept". It is not clear that this is a maximum value for the negotiation phase, so 1) you do not have to worry about setting it too high on the Linux client, as the server will not reject it but negotiate it down if necessary (is that true?), and 2) the negotiation result may actually be much lower than the value you requested, but that is fine, as it wasn't really a hard request, but a soft petition. I suggest that you guys rephrase that man page, in order to prevent other people scratching their heads again. I would write something along this line: "Maximum amount of data that the kernel will negotiate for read [or write] requests in bytes. Maximum size that servers will negotiate is typically ...". By the way, the current option naming is quite misleading too. I am guessing that you can specify "wsize=xxx" and then "mount -l" will show "wsize=yyy", leaving you wondering why your value was not actually taken. Or, like it happened this time, other people automatically assume that I specified a wsize, when I didn't. I would have called these parameters "maxwsize" and "negotiatedwsize", to make the distinction clear. I wonder if it is not too late to change the name of the one listed by "mount -l", that is, the "negotiatedwsize". Regards, rdiez
