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

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.

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 >> -- >> Crash-utility mailing list -- devel(a)lists.crash-utility.osci.io >> To unsubscribe send an email to devel-leave(a)lists.crash-utility.osci.io >> https://${domain_name}/admin/lists/devel.lists.crash-utility.osci.io/ >> Contribution Guidelines: https://github.com/crash-utility/crash/wiki