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afs: Fix total-length calculation for multiple-page send

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Fix the total-length calculation in afs_make_call() when the operation
being dispatched has data from a series of pages attached.

Despite the patched code looking like that it should reduce mathematically
to the current code, it doesn't because the 32-bit unsigned arithmetic
being used to calculate the page-offset-difference doesn't correctly extend
to a 64-bit value when the result is effectively negative.

Without this, some FS.StoreData operations that span multiple pages fail,
reporting too little or too much data.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2017-11-02 15:27:51 +00:00
parent 5f0fc8ba6a
commit 1199db6035
1 changed files with 11 additions and 2 deletions
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13
fs/afs/rxrpc.c
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@ -350,8 +350,17 @@ long afs_make_call(struct afs_addr_cursor *ac, struct afs_call *call,
*/
tx_total_len = call->request_size;
if (call->send_pages) {
tx_total_len += call->last_to - call->first_offset;
tx_total_len += (call->last - call->first) * PAGE_SIZE;
if (call->last == call->first) {
tx_total_len += call->last_to - call->first_offset;
} else {
/* It looks mathematically like you should be able to
* combine the following lines with the ones above, but
* unsigned arithmetic is fun when it wraps...
*/
tx_total_len += PAGE_SIZE - call->first_offset;
tx_total_len += call->last_to;
tx_total_len += (call->last - call->first - 1) * PAGE_SIZE;
}
}
/* create a call */