https://bugzilla.kernel.org/show_bug.cgi?id=27912 Summary: Set 'err' in ext4_init_fs() if kset_create_and_add() fails Product: File System Version: 2.5 Kernel Version: 2.6.38-rc2 Platform: All OS/Version: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: ext4 AssignedTo: fs_ext4@xxxxxxxxxxxxxxxxxxxx ReportedBy: dame_eugene@xxxxxxx Regression: No Set 'err' in ext4_init_fs() if kset_create_and_add() fails ------------------------ In ext4_init_fs() (super.c), consider the following fragment: ext4_kset = kset_create_and_add("ext4", NULL, fs_kobj); if (!ext4_kset) goto out4; If kset_create_and_add() fails for some reason, 'err' variable will remain 0, so ext4_init_fs() will return 0 despite this failure. It will look like as if the module has initialized itself successfully while it has not. On my system this results in a kernel oops as soon as I try to unload ext4 module. To be exact, when destroy_inodecache() is invoked, it tries to call kmem_cache_destroy(ext4_inode_cachep) but ext4_inode_cachep is NULL because it was not initialized due to that incomplete init. So, BUG_ON(!cachep || in_interrupt()) triggers in kmem_cache_destroy(). The problem can be reproduced as follows (it is assumed that ext4 is compiled as a module): load ext4.ko, unload it and then load it again. For some reason, /sys/fs/ext4/ directory is not deleted when the module is unloaded and that is why kset_create_and_add() fails when I try to load it the second time. From the system log: --------------------------------- [ 3077.802232] WARNING: at /home/eugene/distrib/kernel/mainline.git/linux-2.6/fs/sysfs/dir.c:455 sysfs_add_one+0x8a/0xb0() [ 3077.802236] Hardware name: VirtualBox [ 3077.802239] sysfs: cannot create duplicate filename '/fs/ext4' [ 3077.802242] Modules linked in: ext4(+) jbd2 crc16 kedr_controller kedr_fsim_indicator_kmalloc kedr_fsim_indicator_common kedr_fsim_user_space_access kedr_fsim_cmm kedr_fault_simulation kedr_trace kedr_base fuse snd_pcm_oss snd_mixer_oss snd_seq snd_seq_device edd af_packet mperf loop dm_mod snd_intel8x0 snd_ac97_codec ac97_bus e1000 snd_pcm snd_timer ppdev button sg snd soundcore snd_page_alloc parport_pc sr_mod parport cdrom i2c_piix4 ac pcspkr ohci_hcd ehci_hcd usbcore rtc_cmos sd_mod rtc_core rtc_lib fan processor ata_generic thermal thermal_sys hwmon ata_piix ahci libahci libata scsi_mod [last unloaded: kedr_base] [ 3077.802275] Pid: 5388, comm: modprobe Not tainted 2.6.38-rc2-testbox+ #1 [ 3077.802278] Call Trace: [ 3077.802286] [<c02450fd>] ? warn_slowpath_common+0x6d/0xa0 [ 3077.802290] [<c035267a>] ? sysfs_add_one+0x8a/0xb0 [ 3077.802293] [<c035267a>] ? sysfs_add_one+0x8a/0xb0 [ 3077.802298] [<c02451ae>] ? warn_slowpath_fmt+0x2e/0x30 [ 3077.802301] [<c035267a>] ? sysfs_add_one+0x8a/0xb0 [ 3077.802305] [<c03526fc>] ? create_dir+0x5c/0xa0 [ 3077.802309] [<c03527de>] ? sysfs_create_dir+0x6e/0xa0 [ 3077.802314] [<c03d337d>] ? kobject_add_internal+0x9d/0x230 [ 3077.802318] [<c03dd383>] ? kvasprintf+0x43/0x60 [ 3077.802322] [<c03d3a87>] ? kset_register+0x27/0x60 [ 3077.802326] [<c03d3b27>] ? kset_create_and_add+0x67/0xa0 [ 3077.802336] [<f8fc4143>] ? ext4_init_fs+0x37/0x114 [ext4] [ 3077.802340] [<c0201230>] ? do_one_initcall+0x30/0x170 [ 3077.802349] [<f8fc410c>] ? ext4_init_fs+0x0/0x114 [ext4] [ 3077.802354] [<c0278936>] ? sys_init_module+0x116/0x19c0 [ 3077.802359] [<c0202ddc>] ? sysenter_do_call+0x12/0x28 [ 3077.802362] ---[ end trace 8b7776f89b6ab60b ]--- [ 3077.802367] kobject_add_internal failed for ext4 with -EEXIST, don't try to register things with the same name in the same directory. [ 3077.802371] Pid: 5388, comm: modprobe Tainted: G W 2.6.38-rc2-testbox+ #1 [ 3077.802374] Call Trace: [ 3077.802378] [<c03d3434>] ? kobject_add_internal+0x154/0x230 [ 3077.802382] [<c03dd383>] ? kvasprintf+0x43/0x60 [ 3077.802386] [<c03d3a87>] ? kset_register+0x27/0x60 [ 3077.802389] [<c03d3b27>] ? kset_create_and_add+0x67/0xa0 [ 3077.802398] [<f8fc4143>] ? ext4_init_fs+0x37/0x114 [ext4] [ 3077.802402] [<c0201230>] ? do_one_initcall+0x30/0x170 [ 3077.802411] [<f8fc410c>] ? ext4_init_fs+0x0/0x114 [ext4] [ 3077.802416] [<c0278936>] ? sys_init_module+0x116/0x19c0 [ 3077.802420] [<c0202ddc>] ? sysenter_do_call+0x12/0x28 --------------------------------- I suppose a trivial change in ext4_init_fs() would be enough to fix this problem: ext4_kset = kset_create_and_add("ext4", NULL, fs_kobj); if (!ext4_kset) { err = -EEXIST; goto out4; } Not sure about which error code to return though. As far as I can see from the code, kset_create_and_add() can fail due to other reasons as well (out of memory conditions, for example). Besides that, it is still unclear to me why that sysfs directory is not deleted when ext4.ko is unloaded. kset_unregister(ext4_kset) seems to be in place in ext4_exit_fs(). I could probably analyze this a bit further. Anyway, it is another story. Should I file another bug for this? -- Configure bugmail: https://bugzilla.kernel.org/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are watching the assignee of the bug. -- 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
