[Crash-utility] Re: [PATCH] Fix "kmem -i" and "swap" commands on Linux 6.10-rc1 and later kernels

Date: Fri, 28 Jun 2024 13:13:57 +1200 From: Tao Liu <ltao(a)redhat.com&gt; Subject: [Crash-utility] Re: [PATCH] Fix "kmem -i" and "swap" commands on Linux 6.10-rc1 and later kernels To: HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab(a)nec.com&gt; Cc: &quot;devel(a)lists.crash-utility.osci.io&quot; <devel(a)lists.crash-utility.osci.io&gt; Message-ID: < CAO7dBbUHmo0tpaFyAGqeYHBai5PqzT+HSHEUsgimtG4asohVgQ(a)mail.gmail.com&gt; Content-Type: text/plain; charset="UTF-8" Hi Kazu, On Fri, Jun 28, 2024 at 12:41 PM HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab(a)nec.com&gt; wrote: > > Hi Tao, > > thank you for your review. > > On 2024/06/28 9:19, Tao Liu wrote: > > Hi Kazu, > > > > sorry for the late response. > > > > On Tue, Jun 11, 2024 at 2:41 PM HAGIO KAZUHITO(萩尾 一仁) > > <k-hagio-ab(a)nec.com&gt; wrote: > >> > >> Kernel commit 798cb7f9aec3 ("swapon(2)/swapoff(2): don't bother with > >> block size") removed swap_info_struct.old_block_size member at Linux > >> 6.10-rc1. The crash-utility has used this to determine whether a swap > >> is a partition or file and to determine the way to get the swap path. > >> > >> Withtout the patch, the "kmem -i" and "swap" commands fail with the > >> following error messsage: > >> > >> crash> kmem -i > >> ... > >> TOTAL HUGE 13179392 50.3 GB ---- > >> HUGE FREE 13179392 50.3 GB 100% of TOTAL HUGE > >> > >> swap: invalid (optional) structure member offsets: swap_info_struct_swap_device or swap_info_struct_old_block_size > >> FILE: memory.c LINE: 16032 FUNCTION: dump_swap_info() > >> > >> The swap_file member of recent swap_info_struct is a pointer to a > >> struct file (once upon a time it was dentry), use this fact directly. > >> > >> Signed-off-by: Kazuhito Hagio <k-hagio-ab(a)nec.com&gt; > >> --- > >> NOTE: This patch can be applied on top of my '[PATCH] Fix "kmem -v" > >> option on Linux 6.9 and later kernels' patch. Otherwise, please adjust > >> the hunk for offset_table. > >> > >> defs.h | 1 + > >> filesys.c | 1 + > >> memory.c | 28 +++++++++++++++++++++++----- > >> symbols.c | 1 + > >> 4 files changed, 26 insertions(+), 5 deletions(-) > >> > >> diff --git a/defs.h b/defs.h > >> index 95de33188070..64bf785b7a1b 100644 > >> --- a/defs.h > >> +++ b/defs.h > >> @@ -2242,6 +2242,7 @@ struct offset_table { /* stash of commonly-used offsets */ > >> long log_caller_id; > >> long vmap_node_busy; > >> long rb_list_head; > >> + long file_f_inode; > >> }; > >> > >> struct size_table { /* stash of commonly-used sizes */ > >> diff --git a/filesys.c b/filesys.c > >> index 81fe856699e1..406ebb299780 100644 > >> --- a/filesys.c > >> +++ b/filesys.c > >> @@ -2038,6 +2038,7 @@ vfs_init(void) > >> MEMBER_OFFSET_INIT(file_f_dentry, "file", "f_dentry"); > >> MEMBER_OFFSET_INIT(file_f_vfsmnt, "file", "f_vfsmnt"); > >> MEMBER_OFFSET_INIT(file_f_count, "file", "f_count"); > >> + MEMBER_OFFSET_INIT(file_f_inode, "file", "f_inode"); > >> MEMBER_OFFSET_INIT(path_mnt, "path", "mnt"); > >> MEMBER_OFFSET_INIT(path_dentry, "path", "dentry"); > >> if (INVALID_MEMBER(file_f_dentry)) { > >> diff --git a/memory.c b/memory.c > >> index acb8507cfb75..28f901f16adf 100644 > >> --- a/memory.c > >> +++ b/memory.c > >> @@ -16075,6 +16075,8 @@ dump_swap_info(ulong swapflags, ulong *totalswap_pages, ulong *totalused_pages) > >> char buf3[BUFSIZE]; > >> char buf4[BUFSIZE]; > >> char buf5[BUFSIZE]; > >> + int swap_file_is_file = > >> + STREQ(MEMBER_TYPE_NAME("swap_info_struct", "swap_file"), "file"); > >> > >> if (!symbol_exists("nr_swapfiles")) > >> error(FATAL, "nr_swapfiles doesn't exist in this kernel!\n"); > >> @@ -16118,9 +16120,21 @@ dump_swap_info(ulong swapflags, ulong *totalswap_pages, ulong *totalused_pages) > >> swap_file = ULONG(vt->swap_info_struct + > >> OFFSET(swap_info_struct_swap_file)); > >> > >> - swap_device = INT(vt->swap_info_struct + > >> - OFFSET_OPTION(swap_info_struct_swap_device, > >> - swap_info_struct_old_block_size)); > >> + /* Linux 6.10 and later */ > >> + if (INVALID_MEMBER(swap_info_struct_swap_device) && > >> + INVALID_MEMBER(swap_info_struct_old_block_size) && > >> + swap_file_is_file) { > >> + ulong inode; > >> + ushort mode; > >> + readmem(swap_file + OFFSET(file_f_inode), KVADDR, &inode, > >> + sizeof(ulong), "swap_file.f_inode", FAULT_ON_ERROR); > >> + readmem(inode + OFFSET(inode_i_mode), KVADDR, &mode, > >> + sizeof(ushort), "inode.i_mode", FAULT_ON_ERROR); > >> + swap_device = S_ISBLK(mode); > >> + } else > >> + swap_device = INT(vt->swap_info_struct + > >> + OFFSET_OPTION(swap_info_struct_swap_device, > >> + swap_info_struct_old_block_size)); > >> > > > > The above code change is OK to me, just my curiosity: it looks to me > > the swap_file->f_inode->i_mode->S_ISBLK approach will always work, not > > only for the Linux 6.10 and later versions right? E.g. I made the > > following change which works as expected on a 4.0.4-201 kernel: > > This S_ISBLK approach will work with kernels that swap_file is 'file', > and at least 2.6.0 and later kernels have it, as far as I checked (as > written in [1]). > > but I didn't want to change the current behavior (the else block) for > 6.9 and older kernels, because it has worked well with them for a long > time and there is no need to change. > OK, ageed. Thanks a lot for your explanation! The patch is good to me, so ack.

Thanks, Tao Liu > Does this answer your question? > > [1] > https://lists.crash-utility.osci.io/archives/list/devel@lists.crash-utili... > > Thanks, > Kazu > > > > > @@ -16121,9 +16121,7 @@ dump_swap_info(ulong swapflags, ulong > > *totalswap_pages, ulong *totalused_pages) > > OFFSET(swap_info_struct_swap_file)); > > > > /* Linux 6.10 and later */ > > - if (INVALID_MEMBER(swap_info_struct_swap_device) && > > - INVALID_MEMBER(swap_info_struct_old_block_size) && > > - swap_file_is_file) { > > + if (1) { > > ulong inode; > > ushort mode; > > readmem(swap_file + OFFSET(file_f_inode), > > KVADDR, &inode, > > > > KERNEL: burn.khw2.lab.eng.bos.redhat.com/4.0.4-201.fc21_sysrq-c/vmlinux.gz > > DUMPFILE: burn.khw2.lab.eng.bos.redhat.com/4.0.4-201.fc21_sysrq-c/vmcore > > [PARTIAL DUMP] > > CPUS: 4 > > DATE: Wed May 27 14:23:22 EDT 2015 > > UPTIME: 02:47:56 > > LOAD AVERAGE: 0.00, 0.04, 0.05 > > TASKS: 135 > > NODENAME: dell-pec5125-04.lab.bos.redhat.com > > RELEASE: 4.0.4-201.fc21.x86_64 > > VERSION: #1 SMP Thu May 21 15:58:47 UTC 2015 > > MACHINE: x86_64 (2599 Mhz) > > MEMORY: 2 GB > > PANIC: "sysrq: SysRq : Trigger a crash" > > PID: 14037 > > COMMAND: "bash" > > TASK: ffff88006a03d970 [THREAD_INFO: ffff880074734000] > > CPU: 1 > > STATE: TASK_RUNNING (SYSRQ) > > > > crash> swap > > SWAP_INFO_STRUCT TYPE SIZE USED PCT PRI FILENAME > > ffff88007bf62000 PARTITION 2097148k 0k 0% -1 /dev/dm-1 > > crash> kmem -i > > PAGES TOTAL PERCENTAGE > > TOTAL MEM 445983 1.7 GB ---- > > FREE 275307 1.1 GB 61% of TOTAL MEM > > ... > > > > Thanks, > > Tao Liu > > > >> pages = INT(vt->swap_info_struct + > >> OFFSET(swap_info_struct_pages)); > >> @@ -16161,8 +16175,12 @@ dump_swap_info(ulong swapflags, ulong *totalswap_pages, ulong *totalused_pages) > >> OFFSET(swap_info_struct_swap_vfsmnt)); > >> get_pathname(swap_file, buf, BUFSIZE, > >> 1, vfsmnt); > >> - } else if (VALID_MEMBER > >> - (swap_info_struct_old_block_size)) { > >> + } else if (VALID_MEMBER(swap_info_struct_old_block_size) || > >> + swap_file_is_file) { > >> + /* > >> + * Linux 6.10 and later kernels do not have old_block_size, > >> + * but this still should work, if swap_file is file. > >> + */ > >> devname = vfsmount_devname(file_to_vfsmnt(swap_file), > >> buf1, BUFSIZE); > >> get_pathname(file_to_dentry(swap_file), > >> diff --git a/symbols.c b/symbols.c > >> index 283b98a8fbfe..0bf050ab62d0 100644 > >> --- a/symbols.c > >> +++ b/symbols.c > >> @@ -10522,6 +10522,7 @@ dump_offset_table(char *spec, ulong makestruct) > >> OFFSET(file_f_count)); > >> fprintf(fp, " file_f_path: %ld\n", > >> OFFSET(file_f_path)); > >> + fprintf(fp, " file_f_inode: %ld\n", OFFSET(file_f_inode)); > >> fprintf(fp, " path_mnt: %ld\n", > >> OFFSET(path_mnt)); > >> fprintf(fp, " path_dentry: %ld\n", > >> -- > >> 2.31.1