On 02/06/2015 06:28 PM, Omar Sandoval wrote: > On Thu, Feb 05, 2015 at 03:30:47PM -0600, Chris J Arges wrote: >> On 02/05/2015 02:50 PM, Omar Sandoval wrote: >>> Commit 4f579ae7de56 (ext4: fix punch hole on files with indirect >>> mapping) rewrote FALLOC_FL_PUNCH_HOLE for ext4 files with indirect >>> mapping. However, the case where the punch happens within one level of >>> indirection is incorrect. It assumes that the partial branches returned >>> from ext4_find_shared will have the same depth, but this is not >>> necessarily the case even when the offsets have the same depth. For >>> example, if the last block occurs at the beginning of an indirect group >>> (i.e., it has an offset of 0 at the end of the offsets array), then >>> ext4_find_shared will return a shallower chain. So, let's handle the >>> mismatch and clean up that case. Tested with generic/270, which no >>> longer leads to an inconsistent filesystem like before. >>> >>> Signed-off-by: Omar Sandoval <osandov@xxxxxxxxxxx> >> >> >> Omar, >> >> Tried running this with my original reproducer (qcow2 snapshotting and >> rebooting) and got the following: >> ------------[ cut here ]------------ >> kernel BUG at fs/ext4/indirect.c:1488! >> invalid opcode: 0000 [#1] SMP >> <snip> >> CPU: 4 PID: 9771 Comm: qemu-img Tainted: G W E >> 3.19.0-rc7-b164aa5 #22 >> Hardware name: XXX >> task: ffff880243a34aa0 ti: ffff880240f3c000 task.ti: ffff880240f3c000 >> RIP: 0010:[<ffffffff812a38e7>] [<ffffffff812a38e7>] >> ext4_ind_remove_space+0x737/0x740 >> RSP: 0018:ffff880240f3fc98 EFLAGS: 00010246 >> RAX: ffff880240f3fd98 RBX: ffff880240f3fd98 RCX: ffff880098c684dc >> RDX: ffff880098c684d4 RSI: ffff880240f3fd08 RDI: ffff880098c684e0 >> RBP: ffff880240f3fdf8 R08: ffff880098c684e0 R09: 0000000000000000 >> R10: ffff880240f3faa0 R11: 0000000000000038 R12: ffff88009bb65810 >> R13: 0000000000000003 R14: ffff880240f3fd08 R15: ffff880240f3fd68 >> FS: 00007f7ad84ad700(0000) GS:ffff88024e500000(0000) knlGS:0000000000000000 >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> CR2: 00007f7ae19a78ff CR3: 0000000241c52000 CR4: 00000000003427e0 >> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> Stack: >> ffffea0002596600 ffff88009bb65960 0000000000000050 0000000000000100 >> ffff8802447a2900 0000000000000003 ffff880240f3fd08 ffff88009b96c030 >> ffff880240f3fd08 000000000000024b 000000000000000d ffff880000000034 >> Call Trace: >> [<ffffffff8129ccdc>] ? ext4_discard_preallocations+0x16c/0x480 >> [<ffffffff8126982f>] ext4_punch_hole+0x3bf/0x430 >> [<ffffffff81293c9e>] ext4_fallocate+0x16e/0x8c0 >> [<ffffffff811e4849>] ? __sb_start_write+0x49/0xf0 >> [<ffffffff811df3cf>] vfs_fallocate+0x12f/0x250 >> [<ffffffff810eda41>] ? SyS_futex+0x71/0x150 >> [<ffffffff811e0408>] SyS_fallocate+0x48/0x80 >> [<ffffffff8177cc2d>] system_call_fastpath+0x16/0x1b >> Code: 40 4c 8d 0c c5 e8 ff ff ff 49 c1 f9 03 45 69 c9 ab aa aa aa e8 6b >> e2 ff ff 48 8b 85 10 ff ff ff c7 00 00 00 00 00 e9 fd fa ff ff <0f> 0b >> 0f 0b 0f 1f 44 00 00 0f 1f 44 00 00 55 48 89 e5 41 56 41 >> RIP [<ffffffff812a38e7>] ext4_ind_remove_space+0x737/0x740 >> RSP <ffff880240f3fc98> >> ---[ end trace 05f053fdd5d908a8 ]--- >> >> So this is hitting the BUG_ON you added. >> --chris >> > > Chris, > > Would you mind sending over your exact reproduction steps? I've cooked > up a patch which appears to be working, but I want to test it out a bit > more before I send it out. > > Thanks, > Omar, To reproduce this issue do the following: 1) Setup ext4 ^extents, or ext3 filesystem with CONFIG_EXT4_USE_FOR_EXT23=y 2) Create and install a VM using a qcow2 image and store the file on the filesystem 3) Snapshot the image with qemu-img 4) Boot the image and do some disk operations (fio,etc) 5) Shutdown image and delete snapshot 6) Repeat 3-5 until VM no longer boots due to image corruption, generally this takes a few iterations depending on disk operations. I have the reproducer ready to go on my system to feel free to send me a preliminary patch and I'll test it again over the weekend. Thanks, --chris j arges -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
