mirror of
https://github.com/ibm-s390-linux/s390-tools.git
synced 2026-08-05 02:14:52 +00:00
b6c30404bc
The function copy_table_entry_write() maps/unmaps /proc/vmcore for each 64kB of the file in order to write its content to a dump partition. This requires a page allocation of order 2 in kernel (crst_table_alloc) each time a mmap() syscall is performed and which cannot always be fulfilled due to external memory fragmentation. And this in turn results in a OOM kernel panic while writing /proc/vmcore content to a dump partition. To make zfcpdump more robust in the face of such problems with page allocations of order > 0, we use a simple file read/write loop to transfer the content of /proc/vmcore to a dump partition. This solution is less efficient (by not much) than the old one with mmap() because it requires additional user space copy but we trade off here efficiency for robustness which is more important for zfcpdump. We use a statically allocated buffer to read data into from /proc/vmcore and write to a dump partition to avoid repeated use of the memory mapping kernel path which would be required for a buffer allocated dynamically at each entry of copy_table_entry_write(). Another possible and very convenient solution would be to use sendfile() which would avoid any user space copies but, unfortunately, sendfile() doesn't work with large /proc files. Example of failed mmap() call for /proc/vmcore ============================================== [ 26.568654] init invoked oom-killer: gfp_mask=0x40cc0(GFP_KERNEL|__GFP_COMP), order=2, oom_score_adj=0 [ 26.568665] CPU: 0 PID: 1 Comm: init Not tainted 6.9.0-20240504.rc6.git0.9986ea583f39.300.fc39.s390x+zfcpdump #1 [ 26.568668] Hardware name: IBM 3931 A01 704 (LPAR) [ 26.568669] Call Trace: [ 26.568671] [<000003ffe03277c6>] dump_stack_lvl+0x76/0x98 [ 26.568676] [<000003ffe00f15c8>] dump_header+0x58/0x2d0 [ 26.568680] [<000003ffe00f219a>] out_of_memory+0x252/0x348 [ 26.568683] [<000003ffe0132f3e>] __alloc_pages_slowpath.constprop.0+0x65e/0x7c0 [ 26.568686] [<000003ffe01331a4>] __alloc_pages+0x104/0x128 [ 26.568688] [<000003ffe001ab46>] crst_table_alloc+0x2e/0xa0 [ 26.568693] [<000003ffe01164c4>] __pmd_alloc+0x24/0x160 [ 26.568696] [<000003ffe0116650>] pmd_alloc+0x50/0x68 [ 26.568698] [<000003ffe0117be4>] remap_pfn_range_notrack+0x194/0x310 [ 26.568701] [<000003ffe0117d7c>] remap_pfn_range+0x1c/0x28 [ 26.568703] [<000003ffe0015442>] remap_oldmem_pfn_range+0xb2/0x108 [ 26.568705] [<000003ffe01a0544>] mmap_vmcore+0x414/0x448 [ 26.568707] [<000003ffe01937c4>] proc_reg_mmap+0x84/0xa0 [ 26.568709] [<000003ffe011f264>] mmap_region+0x22c/0x6f8 [ 26.568711] [<000003ffe011fae8>] do_mmap+0x3b8/0x410 [ 26.568713] [<000003ffe01015cc>] vm_mmap_pgoff+0x9c/0xe8 [ 26.568715] [<000003ffe011d006>] ksys_mmap_pgoff+0x8e/0xb8 [ 26.568716] [<000003ffe011d0f4>] __s390x_sys_old_mmap+0x74/0x90 [ 26.568718] [<000003ffe0341a2a>] __do_syscall+0x1aa/0x220 [ 26.568720] [<000003ffe03478b0>] system_call+0x70/0x98 [ 26.568724] Mem-Info: [ 26.568725] active_anon:1 inactive_anon:12 isolated_anon:0 active_file:83590 inactive_file:93939 isolated_file:0 unevictable:201 dirty:17845 writeback:4 slab_reclaimable:4259 slab_unreclaimable:1482 mapped:174 shmem:0 pagetables:810 sec_pagetables:0 bounce:0 kernel_misc_reclaimable:0 free:2694 free_pcp:105 free_cma:0 [ 26.568729] Node 0 active_anon:4kB inactive_anon:48kB active_file:334360kB inactive_file:375756kB unevictable:804kB isolated(anon):0kB isolated(file):0kB mapped:696kB dirty:71380kB writeback:16kB shmem:0kB writeback_tmp:0kB kernel_stack:544kB pagetables:3240kB sec_pagetables:0kB all_unreclaimable? no [ 26.568732] DMA free:10776kB boost:0kB min:3496kB low:4368kB high:5240kB reserved_highatomic:0KB active_anon:4kB inactive_anon:48kB active_file:334360kB inactive_file:375756kB unevictable:804kB writepending:71360kB present:786428kB managed:764664kB mlocked:0kB bounce:0kB free_pcp:420kB local_pcp:420kB free_cma:0kB [ 26.568735] lowmem_reserve[]: 0 0 0 [ 26.568738] DMA: 1069*4kB (UH) 757*8kB (UH) 11*16kB (H) 6*32kB (H) 1*64kB (H) 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 10764kB [ 26.568747] 177773 total pagecache pages [ 26.568748] 196607 pages RAM [ 26.568748] 0 pages HighMem/MovableOnly [ 26.568749] 5441 pages reserved [ 26.568749] Tasks state (memory values in pages): [ 26.568750] [ pid ] uid tgid total_vm rss rss_anon rss_file rss_shmem pgtables_bytes swapents oom_score_adj name [ 26.568751] Out of memory and no killable processes... [ 26.568752] Kernel panic - not syncing: System is deadlocked on memory [ 26.568755] CPU: 0 PID: 1 Comm: init Not tainted 6.9.0-20240504.rc6.git0.9986ea583f39.300.fc39.s390x+zfcpdump #1 [ 26.568758] Hardware name: IBM 3931 A01 704 (LPAR) [ 26.568759] Call Trace: [ 26.568760] [<000003ffe03277c6>] dump_stack_lvl+0x76/0x98 [ 26.568763] [<000003ffe001f14e>] panic+0x10e/0x2e8 [ 26.568765] [<000003ffe00f21c8>] out_of_memory+0x280/0x348 [ 26.568768] [<000003ffe0132f3e>] __alloc_pages_slowpath.constprop.0+0x65e/0x7c0 [ 26.568771] [<000003ffe01331a4>] __alloc_pages+0x104/0x128 [ 26.568773] [<000003ffe001ab46>] crst_table_alloc+0x2e/0xa0 [ 26.568776] [<000003ffe01164c4>] __pmd_alloc+0x24/0x160 [ 26.568779] [<000003ffe0116650>] pmd_alloc+0x50/0x68 [ 26.568781] [<000003ffe0117be4>] remap_pfn_range_notrack+0x194/0x310 [ 26.568784] [<000003ffe0117d7c>] remap_pfn_range+0x1c/0x28 [ 26.568787] [<000003ffe0015442>] remap_oldmem_pfn_range+0xb2/0x108 [ 26.568789] [<000003ffe01a0544>] mmap_vmcore+0x414/0x448 [ 26.568791] [<000003ffe01937c4>] proc_reg_mmap+0x84/0xa0 [ 26.568793] [<000003ffe011f264>] mmap_region+0x22c/0x6f8 [ 26.568795] [<000003ffe011fae8>] do_mmap+0x3b8/0x410 [ 26.568797] [<000003ffe01015cc>] vm_mmap_pgoff+0x9c/0xe8 [ 26.568799] [<000003ffe011d006>] ksys_mmap_pgoff+0x8e/0xb8 [ 26.568801] [<000003ffe011d0f4>] __s390x_sys_old_mmap+0x74/0x90 [ 26.568803] [<000003ffe0341a2a>] __do_syscall+0x1aa/0x220 [ 26.568805] [<000003ffe03478b0>] system_call+0x70/0x98 Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com> Reviewed-by: Mikhail Zaslonko <zaslonko@linux.ibm.com> Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
zfcpdump: S390 SCSI dump tool (Version 3) ========================================= zfcpdump is used for creating System dumps for Linux on System z. It has two parts: a zfcpdump enabled Linux kernel and a user space application. This is the 3rd version of zfcpdump which uses the upstream kernel version 3.12 or above. This version writes the dump to a partition in contrast to the previous versions where the dump was written to a file system. The user space application of zfcpdump can reside either in an intitramfs or an initrd. It reads from /proc/vmcore, provided by the kernel part, and writes the system dump to a SCSI disk partition. To build a zfcpdump enabled kernel use the following settings in your kernel configuration: * CONFIG_ZFCPDUMP=y * CONFIG_BLK_DEV_INITRD=y * CONFIG_EFI_PARTITION=y for using GPT disk layout * CONFIG_MSDOS_PARTITION=y for using MSDOS disk layout * BLK_DEV_SD=y * Enable ZFCP driver * Enable SCSI driver * Disable as many features as possible to keep the kernel small. E.g. network and file system support is not needed at all. You can use "make zfcpdump_defconfig" as a starting point for your kernel configuration. * Issue "make bzImage" to build the zfcpdump kernel image. In a Linux distribution the zfcpdump enabled kernel image must be copied to /lib/s390-tools/zfcpdump/zfcpdump-image, where the s390 zipl tool is looking for the dump kernel when preparing a SCSI dump disk. Create and install initrd ========================= * make Builds "cpioinit" and statically linked "zfcpdump" application. Then cpioinit is used to integrate the zfcpdump application into the cpio archive zfcpdump_part.rd. * make install The initrd zfcpdump_part.rd is installed to "/lib/s390-tools/zfcpdump/". Additional information ====================== For more information on how to use zfcpdump and zipl refer to the s390 'Using the Dump Tools' book, which is available from: http://www.ibm.com/developerworks/linux/linux390.