diff options
| -rw-r--r-- | block/file-posix.c | 36 |
1 files changed, 25 insertions, 11 deletions
diff --git a/block/file-posix.c b/block/file-posix.c index 4479cc7ab4..b8b4dad553 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -323,6 +323,7 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp) BDRVRawState *s = bs->opaque; char *buf; size_t max_align = MAX(MAX_BLOCKSIZE, getpagesize()); + size_t alignments[] = {1, 512, 1024, 2048, 4096}; /* For SCSI generic devices the alignment is not really used. With buffered I/O, we don't have any restrictions. */ @@ -349,25 +350,38 @@ static void raw_probe_alignment(BlockDriverState *bs, int fd, Error **errp) } #endif - /* If we could not get the sizes so far, we can only guess them */ - if (!s->buf_align) { + /* + * If we could not get the sizes so far, we can only guess them. First try + * to detect request alignment, since it is more likely to succeed. Then + * try to detect buf_align, which cannot be detected in some cases (e.g. + * Gluster). If buf_align cannot be detected, we fallback to the value of + * request_alignment. + */ + + if (!bs->bl.request_alignment) { + int i; size_t align; - buf = qemu_memalign(max_align, 2 * max_align); - for (align = 512; align <= max_align; align <<= 1) { - if (raw_is_io_aligned(fd, buf + align, max_align)) { - s->buf_align = align; + buf = qemu_memalign(max_align, max_align); + for (i = 0; i < ARRAY_SIZE(alignments); i++) { + align = alignments[i]; + if (raw_is_io_aligned(fd, buf, align)) { + /* Fallback to safe value. */ + bs->bl.request_alignment = (align != 1) ? align : max_align; break; } } qemu_vfree(buf); } - if (!bs->bl.request_alignment) { + if (!s->buf_align) { + int i; size_t align; - buf = qemu_memalign(s->buf_align, max_align); - for (align = 512; align <= max_align; align <<= 1) { - if (raw_is_io_aligned(fd, buf, align)) { - bs->bl.request_alignment = align; + buf = qemu_memalign(max_align, 2 * max_align); + for (i = 0; i < ARRAY_SIZE(alignments); i++) { + align = alignments[i]; + if (raw_is_io_aligned(fd, buf + align, max_align)) { + /* Fallback to request_aligment. */ + s->buf_align = (align != 1) ? align : bs->bl.request_alignment; break; } } |