[{"id":1776629,"web_url":"http://patchwork.ozlabs.org/comment/1776629/","msgid":"<37b21d60-acbd-c4ce-3d6f-3f852b8da2a3@redhat.com>","list_archive_url":null,"date":"2017-09-27T21:35:12","subject":"Re: [Qemu-devel] [PATCH v4 16/23] qemu-img: Drop redundant error\n\tmessage in compare","submitter":{"id":64343,"url":"http://patchwork.ozlabs.org/api/people/64343/","name":"John Snow","email":"jsnow@redhat.com"},"content":"On 09/13/2017 12:03 PM, Eric Blake wrote:\n> If a read error is encountered during 'qemu-img compare', we\n> were printing the \"Error while reading offset ...\" message twice.\n> Update the testsuite for the improved output.\n> \n> Further simplify the code by hoisting the error code conversion\n> into the helper function, rather than repeating it at the callers.\n> \n> Signed-off-by: Eric Blake \n> \n> ---\n> v3: new patch\n> ---\n> qemu-img.c | 19 +++++--------------\n> tests/qemu-iotests/074.out | 2 --\n> 2 files changed, 5 insertions(+), 16 deletions(-)\n> \n> diff --git a/qemu-img.c b/qemu-img.c\n> index dfccebe6bc..3e1e373e8f 100644\n> --- a/qemu-img.c\n> +++ b/qemu-img.c\n> @@ -1196,8 +1196,10 @@ static int64_t sectors_to_bytes(int64_t sectors)\n> /*\n> * Check if passed sectors are empty (not allocated or contain only 0 bytes)\n> *\n> - * Returns 0 in case sectors are filled with 0, 1 if sectors contain non-zero\n> - * data and negative value on error.\n> + * Intended for use by 'qemu-img compare': Returns 0 in case sectors are\n> + * filled with 0, 1 if sectors contain non-zero data (this is a comparison\n> + * failure), and 4 on error (the exit status for read errors), after emitting\n> + * an error message.\n> *\n> * @param blk: BlockBackend for the image\n> * @param sect_num: Number of first sector to check\n> @@ -1218,7 +1220,7 @@ static int check_empty_sectors(BlockBackend *blk, int64_t sect_num,\n> if (ret < 0) {\n> error_report(\"Error while reading offset %\" PRId64 \" of %s: %s\",\n> sectors_to_bytes(sect_num), filename, strerror(-ret));\n> - return ret;\n> + return 4;\n> }\n> idx = find_nonzero(buffer, sect_count * BDRV_SECTOR_SIZE);\n> if (idx >= 0) {\n> @@ -1473,11 +1475,6 @@ static int img_compare(int argc, char **argv)\n> filename2, buf1, quiet);\n> }\n> if (ret) {\n> - if (ret < 0) {\n> - error_report(\"Error while reading offset %\" PRId64 \": %s\",\n> - sectors_to_bytes(sector_num), strerror(-ret));\n> - ret = 4;\n> - }\n> goto out;\n> }\n> }\n> @@ -1522,12 +1519,6 @@ static int img_compare(int argc, char **argv)\n> ret = check_empty_sectors(blk_over, sector_num, nb_sectors,\n> filename_over, buf1, quiet);\n> if (ret) {\n> - if (ret < 0) {\n> - error_report(\"Error while reading offset %\" PRId64\n> - \" of %s: %s\", sectors_to_bytes(sector_num),\n> - filename_over, strerror(-ret));\n> - ret = 4;\n> - }\n> goto out;\n> }\n> }\n> diff --git a/tests/qemu-iotests/074.out b/tests/qemu-iotests/074.out\n> index 8fba5aea9c..ede66c3f81 100644\n> --- a/tests/qemu-iotests/074.out\n> +++ b/tests/qemu-iotests/074.out\n> @@ -4,7 +4,6 @@ Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824\n> wrote 512/512 bytes at offset 512\n> 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)\n> qemu-img: Error while reading offset 0 of blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error\n> -qemu-img: Error while reading offset 0: Input/output error\n> 4\n> Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=1073741824\n> Formatting 'TEST_DIR/t.IMGFMT.2', fmt=IMGFMT size=0\n> @@ -12,7 +11,6 @@ Formatting 'TEST_DIR/t.IMGFMT.2', fmt=IMGFMT size=0\n> wrote 512/512 bytes at offset 512\n> 512 bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)\n> qemu-img: Error while reading offset 0 of blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error\n> -qemu-img: Error while reading offset 0 of blkdebug:TEST_DIR/blkdebug.conf:TEST_DIR/t.IMGFMT: Input/output error\n> Warning: Image size mismatch!\n> 4\n> Cleanup\n> \n\nHm, naively I might assume it's best for the caller to report the error\nand to leave the function a nicely self-contained helper, but I won't\ninsist on it.\n\nReviewed-by: John Snow ","headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@bilbo.ozlabs.org","Authentication-Results":["ozlabs.org;\n\tspf=pass (mailfrom) smtp.mailfrom=nongnu.org\n\t(client-ip=2001:4830:134:3::11; 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