| Message ID | b757ff64ddf68519fc3d55b66fcd8a1d4b436395.1573467154.git.jstancek@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iomap: fix return value of iomap_dio_bio_actor on 32bit systems | expand |
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
On Mon, Nov 11, 2019 at 11:28:10AM +0100, Jan Stancek wrote: > Naresh reported LTP diotest4 failing for 32bit x86 and arm -next > kernels on ext4. Same problem exists in 5.4-rc7 on xfs. > > The failure comes down to: > openat(AT_FDCWD, "testdata-4.5918", O_RDWR|O_DIRECT) = 4 > mmap2(NULL, 4096, PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f7b000 > read(4, 0xb7f7b000, 4096) = 0 // expects -EFAULT > > Problem is conversion at iomap_dio_bio_actor() return. Ternary > operator has a return type and an attempt is made to convert each > of operands to the type of the other. In this case "ret" (int) > is converted to type of "copied" (unsigned long). Both have size > of 4 bytes: > size_t copied = 0; > int ret = -14; > long long actor_ret = copied ? copied : ret; > > On x86_64: actor_ret == -14; > On x86 : actor_ret == 4294967282 > > Replace ternary operator with 2 return statements to avoid this > unwanted conversion. > > Fixes: 4721a6010990 ("iomap: dio data corruption and spurious errors when pipes fill") > Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> > Signed-off-by: Jan Stancek <jstancek@redhat.com> Thansk for the full explanation & patch, will test... Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> --D > --- > fs/iomap/direct-io.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index 1fc28c2da279..7c58f51d7da7 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -318,7 +318,9 @@ static void iomap_dio_bio_end_io(struct bio *bio) > if (pad) > iomap_dio_zero(dio, iomap, pos, fs_block_size - pad); > } > - return copied ? copied : ret; > + if (copied) > + return copied; > + return ret; > } > > static loff_t > -- > 1.8.3.1 >
diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 1fc28c2da279..7c58f51d7da7 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -318,7 +318,9 @@ static void iomap_dio_bio_end_io(struct bio *bio) if (pad) iomap_dio_zero(dio, iomap, pos, fs_block_size - pad); } - return copied ? copied : ret; + if (copied) + return copied; + return ret; } static loff_t
Naresh reported LTP diotest4 failing for 32bit x86 and arm -next kernels on ext4. Same problem exists in 5.4-rc7 on xfs. The failure comes down to: openat(AT_FDCWD, "testdata-4.5918", O_RDWR|O_DIRECT) = 4 mmap2(NULL, 4096, PROT_READ, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f7b000 read(4, 0xb7f7b000, 4096) = 0 // expects -EFAULT Problem is conversion at iomap_dio_bio_actor() return. Ternary operator has a return type and an attempt is made to convert each of operands to the type of the other. In this case "ret" (int) is converted to type of "copied" (unsigned long). Both have size of 4 bytes: size_t copied = 0; int ret = -14; long long actor_ret = copied ? copied : ret; On x86_64: actor_ret == -14; On x86 : actor_ret == 4294967282 Replace ternary operator with 2 return statements to avoid this unwanted conversion. Fixes: 4721a6010990 ("iomap: dio data corruption and spurious errors when pipes fill") Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Jan Stancek <jstancek@redhat.com> --- fs/iomap/direct-io.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)