Hello. Can someone explain me logic of generic/pending-4.14/411-mtd-partial_eraseblock_write.patch memory management?
hardware: tp-link mr3040 v2 with 16Mb spi-nor flash and 32Mb DDR memory (u-boot by pepe2k), kernel-4.14.171 (OpenWrt GCC 9.2.0 r12470-dfb7a4ce5d) flash organisation: [ 0.568427] m25p80 spi0.0: found w25q128, expected m25p80 [ 0.583650] m25p80 spi0.0: w25q128 (16384 Kbytes) [ 0.587270] 5 tp-link partitions found on MTD device spi0.0 [ 0.592453] Creating 5 MTD partitions on "spi0.0": [ 0.597290] 0x000000000000-0x000000020000 : "u-boot" [ 0.604187] 0x000000020000-0x0000001a75b4 : "kernel" [ 0.607700] mtd: partition "kernel" doesn't end on an erase/write block boundary -- mark MTD_ERASE_PARTIAL [ 0.620231] 0x0000001a75b4-0x000000ff0000 : "rootfs" [ 0.623821] mtd: partition "rootfs" doesn't start on an erase/write block boundary -- mark MTD_ERASE_PARTIAL [ 0.634667] mtd: device 2 (rootfs) set to be root filesystem [ 0.639242] 1 squashfs-split partitions found on MTD device rootfs [ 0.645429] Creating 1 MTD partitions on "rootfs": [ 0.650141] 0x000000468a4c-0x000000e48a4c : "rootfs_data" [ 0.658939] 0x000000ff0000-0x000001000000 : "art" [ 0.664556] 0x000000020000-0x000000ff0000 : "firmware" symptom - board can't survive first boot, invoking OOM killer, crashed later. jffs2 gc thread trigger this. Boot with KMEMLEAK detector show huge leak inside part_erase() . As you see, "rootfs" partition not aligned, so MTD_ERASE_PARTIAL flag is set. squashfs parser (after commit 7703e14bc4f36758ac28eea3c2abce7591ed4b8d) align found partition to near erase block, so "rootfs_data" already aligned. When jffs2 first time mount rootfs it erase free blocks. Typical execution flow is: part_erase() check MTD_ERASE_PARTIAL for "rootfs_data", call parent for erase (itself again, but with "rootfs" mtd partition), check again MTD_ERASE_PARTIAL for "rootfs", allocates 1000h buffer, read need data from device, call mtd->parent again, now parent call spi_nor_erase() to erase block, spi_nor_erase() calls callback mtd_erase_callback() which try to write back halves from buffer and free it when instr->mtd->flags have MTD_ERASE_PARTIAL, return to spi_nor_erase() and unwind all call's back. - is code in 411 patch is correct? It's simple assumes that parent is aligned, slave - is not. And when parent partition (read "rootfs") not aligned, slave (read "rootfs_data") aligned - it simply leak memory in size of "rootfs_data" partition. I think it should check instr->mtd->flags in part_erase() instead of mtd->flags. And why we have two tplink partition parser one in target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_tplink.c and second in target/linux/ar71xx/files/drivers/mtd/tplinkpart.c (with copy in target/linux/ath79/files/drivers/mtd/tplinkpart.c) maybe collapse it into one ? _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel
