Re: [Crash-utility] [PATCH] Fix for "dev" command on Linux 5.11 and later

Hi, Kazu Thank you for the fix. On Wed, Jun 15, 2022 at 8:00 PM <crash-utility-request(a)redhat.com&gt; wrote: > Date: Wed, 15 Jun 2022 01:50:13 +0000 > From: HAGIO KAZUHITO(?????) <k-hagio-ab(a)nec.com&gt; > To: &quot;lijiang(a)redhat.com&quot; <lijiang(a)redhat.com&gt;, > &quot;crash-utility(a)redhat.com&quot; <crash-utility(a)redhat.com&gt; > Subject: [Crash-utility] [PATCH] Fix for "dev" command on Linux 5.11 > and later > Message-ID: <1655257808-3245-1-git-send-email-k-hagio-ab(a)nec.com&gt; > Content-Type: text/plain; charset="iso-2022-jp" > > The following kernel commits eventually removed the bdev_map array in > Linux v5.11 kernel: > > e418de3abcda ("block: switch gendisk lookup to a simple xarray") > 22ae8ce8b892 ("block: simplify bdev/disk lookup in blkdev_get") > > Without the patch, the "dev" command fails to dump block device data > with the following error: > > crash> dev > ... > dev: blkdevs or all_bdevs: symbols do not exist > > To get block device's gendisk, search blockdev_superblock.s_inodes > instead of bdev_map. > > Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > --- > dev.c | 76 +++++++++++++++++++++++++++++++++++++++++++++++++++++++---- > 1 file changed, 71 insertions(+), 5 deletions(-) > > diff --git a/dev.c b/dev.c > index db97f8aebdc2..238dfe0fbe3c 100644 > --- a/dev.c > +++ b/dev.c > @@ -24,6 +24,7 @@ static void dump_blkdevs_v2(ulong); > static void dump_blkdevs_v3(ulong); > static ulong search_cdev_map_probes(char *, int, int, ulong *); > static ulong search_bdev_map_probes(char *, int, int, ulong *); > +static ulong search_blockdev_inodes(int, ulong *); > It could be good to be consistent with the above function name, I would suggest renaming the "search_blockdev_inodes()" to "search_sb_inodes()".

static void do_pci(void); > static void do_pci2(void); > static void do_io(void); > @@ -493,9 +494,10 @@ dump_blkdevs(ulong flags) > ulong ops; > } blkdevs[MAX_DEV], *bp; > > - if (kernel_symbol_exists("major_names") && > - kernel_symbol_exists("bdev_map")) { > - dump_blkdevs_v3(flags); > + if (kernel_symbol_exists("major_names") && > + (kernel_symbol_exists("bdev_map") || > + kernel_symbol_exists("blockdev_superblock"))) { > + dump_blkdevs_v3(flags); > return; > } > > @@ -717,6 +719,7 @@ dump_blkdevs_v3(ulong flags) > char buf[BUFSIZE]; > uint major; > ulong gendisk, addr, fops; > + int use_bdev_map = kernel_symbol_exists("bdev_map"); > > if (!(len = get_array_length("major_names", NULL, 0))) > len = MAX_DEV; > @@ -745,8 +748,11 @@ dump_blkdevs_v3(ulong flags) > strncpy(buf, blk_major_name_buf + > OFFSET(blk_major_name_name), 16); > > - fops = search_bdev_map_probes(buf, major == i ? major : i, > - UNUSED, &gendisk); > + if (use_bdev_map) > + fops = search_bdev_map_probes(buf, major == i ? > major : i, > + UNUSED, &gendisk); > + else /* v5.11 and later */ > + fops = search_blockdev_inodes(major, &gendisk); > > if (CRASHDEBUG(1)) > fprintf(fp, "blk_major_name: %lx block major: %d > name: %s gendisk: %lx fops: %lx\n", > @@ -829,6 +835,66 @@ search_bdev_map_probes(char *name, int major, int > minor, ulong *gendisk) > return fops; > } > > +/* For bdev_inode. See block/bdev.c */ > +#define I_BDEV(inode) (inode - SIZE(block_device)) > + > Good understanding, this is equivalent to the contain_of(). +static ulong > +search_blockdev_inodes(int major, ulong *gendisk) > +{ > + struct list_data list_data, *ld; > + ulong addr, bd_sb, disk, fops = 0; > + int i, inode_count, gendisk_major; > + char *gendisk_buf; > + > + ld = &list_data; > + BZERO(ld, sizeof(struct list_data)); > + > + get_symbol_data("blockdev_superblock", sizeof(void *), &bd_sb); > + > + addr = bd_sb + OFFSET(super_block_s_inodes); > + if (!readmem(addr, KVADDR, &ld->start, sizeof(ulong), > + "blockdev_superblock.s_inodes", QUIET|RETURN_ON_ERROR)) > + return 0; > + > + if (empty_list(ld->start)) > + return 0; > + > + ld->flags |= LIST_ALLOCATE; > + ld->end = bd_sb + OFFSET(super_block_s_inodes); > + ld->list_head_offset = OFFSET(inode_i_sb_list); > + > + inode_count = do_list(ld); > + > + gendisk_buf = GETBUF(SIZE(gendisk)); > + > + for (i = 0; i < inode_count; i++) { > + addr = I_BDEV(ld->list_ptr[i]) + > OFFSET(block_device_bd_disk); > + if (!readmem(addr, KVADDR, &disk, sizeof(ulong), > + "block_device.bd_disk", QUIET|RETURN_ON_ERROR)) > + continue; > + > + if (!disk) > + continue; > + > + if (!readmem(disk, KVADDR, gendisk_buf, SIZE(gendisk), > + "gendisk buffer", QUIET|RETURN_ON_ERROR)) > + continue; > + > + gendisk_major = INT(gendisk_buf + OFFSET(gendisk_major)); > + if (gendisk_major != major) > + continue; > + > + fops = ULONG(gendisk_buf + OFFSET(gendisk_fops)); > + if (fops) { > + *gendisk = disk; > + break; > + } > + } > + > Because the ld->flags is set to LIST_ALLOCATE, here need to free it as below: FREEBUF(ld->list_ptr);