Messages in this thread | | | From | Ming Lei <> | Date | Tue, 28 Mar 2017 19:42:44 +0800 | Subject | Re: [PATCH] Revert "md: raid1: use bio helper in process_checks()" |
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On Tue, Mar 28, 2017 at 7:35 PM, Arnd Bergmann <arnd@arndb.de> wrote: > On Tue, Mar 28, 2017 at 12:44 PM, Ming Lei <tom.leiming@gmail.com> wrote: >> On Tue, Mar 28, 2017 at 5:49 PM, Arnd Bergmann <arnd@arndb.de> wrote: >>> Commit 60928a91b0b3 ("md: raid1: use bio helper in process_checks()") >>> is probably correct, but I get a new compile-time warning after >>> it, and have trouble understanding what it fixes: >>> >>> drivers/md/raid1.c: In function 'sync_request_write': >>> drivers/md/raid1.c:2172:9: error: 'page_len$' may be used uninitialized in this function [-Werror=maybe-uninitialized] >>> if (memcmp(page_address(ppages[j]), >>> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> page_address(spages[j]), >>> ~~~~~~~~~~~~~~~~~~~~~~~~ >>> page_len[j])) >>> ~~~~~~~~~~~~ >>> drivers/md/raid1.c:2160:7: note: 'page_len$' was declared here >>> int page_len[RESYNC_PAGES]; >>> ^~~~~~~~ >>> >>> This reverts it to resolve the warning. >> >> Please try the following patch: >> >> https://lkml.org/lkml/2017/3/28/126 > > > That patch will certainly shut up the warning, but will also prevent > the compiler from warning when the function gets changed in some > way that actually leads to an uninitialized use of the page_len array,
Why do you think that it leads to an uninitialized use of the page_len array?
The following code does initialize the array well enough for future use:
bio_for_each_segment_all(bi, sbio, j) page_len[j] = bi->bv_len;
That is why we don't need to initialize the array explicitly, but just for killing the warning.
Thanks, Ming Lei
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