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bcache: clear BCACHE_DEV_UNLINK_DONE flag when attaching a backing device
This bug can be reproduced by the following script: #!/bin/bash bcache_sysfs="/sys/fs/bcache" function clear_cache() { if [ ! -e $bcache_sysfs ]; then echo "no bcache sysfs" exit fi cset_uuid=$(ls -l $bcache_sysfs|head -n 2|tail -n 1|awk '{print $9}') sudo sh -c "echo $cset_uuid > /sys/block/sdb/sdb1/bcache/detach" sleep 5 sudo sh -c "echo $cset_uuid > /sys/block/sdb/sdb1/bcache/attach" } for ((i=0;i<10;i++)); do clear_cache done The warning messages look like below: [ 275.948611] ------------[ cut here ]------------ [ 275.963840] WARNING: at fs/sysfs/dir.c:512 sysfs_add_one+0xb8/0xd0() (Tainted: P W --------------- ) [ 275.979253] Hardware name: Tecal RH2285 [ 275.994106] sysfs: cannot create duplicate filename '/devices/pci0000:00/0000:00:09.0/0000:08:00.0/host4/target4:2:1/4:2:1:0/block/sdb/sdb1/bcache/cache' [ 276.024105] Modules linked in: bcache tcp_diag inet_diag ipmi_devintf ipmi_si ipmi_msghandler bonding 8021q garp stp llc ipv6 ext3 jbd loop sg iomemory_vsl(P) bnx2 microcode serio_raw i2c_i801 i2c_core iTCO_wdt iTCO_vendor_support i7core_edac edac_core shpchp ext4 jbd2 mbcache megaraid_sas pata_acpi ata_generic ata_piix dm_mod [last unloaded: scsi_wait_scan] [ 276.072643] Pid: 2765, comm: sh Tainted: P W --------------- 2.6.32 #1 [ 276.089315] Call Trace: [ 276.105801] [<ffffffff81070fe7>] ? warn_slowpath_common+0x87/0xc0 [ 276.122650] [<ffffffff810710d6>] ? warn_slowpath_fmt+0x46/0x50 [ 276.139361] [<ffffffff81205c08>] ? sysfs_add_one+0xb8/0xd0 [ 276.156012] [<ffffffff8120609b>] ? sysfs_do_create_link+0x12b/0x170 [ 276.172682] [<ffffffff81206113>] ? sysfs_create_link+0x13/0x20 [ 276.189282] [<ffffffffa03bda21>] ? bcache_device_link+0xc1/0x110 [bcache] [ 276.205993] [<ffffffffa03bfa08>] ? bch_cached_dev_attach+0x478/0x4f0 [bcache] [ 276.222794] [<ffffffffa03c4a17>] ? bch_cached_dev_store+0x627/0x780 [bcache] [ 276.239680] [<ffffffff8116783a>] ? alloc_pages_current+0xaa/0x110 [ 276.256594] [<ffffffff81203b15>] ? sysfs_write_file+0xe5/0x170 [ 276.273364] [<ffffffff811887b8>] ? vfs_write+0xb8/0x1a0 [ 276.290133] [<ffffffff811890b1>] ? sys_write+0x51/0x90 [ 276.306368] [<ffffffff8100c072>] ? system_call_fastpath+0x16/0x1b [ 276.322301] ---[ end trace 9f5d4fcdd0c3edfb ]--- [ 276.338241] ------------[ cut here ]------------ [ 276.354109] WARNING: at /home/wenqing.lz/bcache/bcache/super.c:720 bcache_device_link+0xdf/0x110 [bcache]() (Tainted: P W --------------- ) [ 276.386017] Hardware name: Tecal RH2285 [ 276.401430] Couldn't create device <-> cache set symlinks [ 276.401759] Modules linked in: bcache tcp_diag inet_diag ipmi_devintf ipmi_si ipmi_msghandler bonding 8021q garp stp llc ipv6 ext3 jbd loop sg iomemory_vsl(P) bnx2 microcode serio_raw i2c_i801 i2c_core iTCO_wdt iTCO_vendor_support i7core_edac edac_core shpchp ext4 jbd2 mbcache megaraid_sas pata_acpi ata_generic ata_piix dm_mod [last unloaded: scsi_wait_scan] [ 276.465477] Pid: 2765, comm: sh Tainted: P W --------------- 2.6.32 #1 [ 276.482169] Call Trace: [ 276.498610] [<ffffffff81070fe7>] ? warn_slowpath_common+0x87/0xc0 [ 276.515405] [<ffffffff810710d6>] ? warn_slowpath_fmt+0x46/0x50 [ 276.532059] [<ffffffffa03bda3f>] ? bcache_device_link+0xdf/0x110 [bcache] [ 276.548808] [<ffffffffa03bfa08>] ? bch_cached_dev_attach+0x478/0x4f0 [bcache] [ 276.565569] [<ffffffffa03c4a17>] ? bch_cached_dev_store+0x627/0x780 [bcache] [ 276.582418] [<ffffffff8116783a>] ? alloc_pages_current+0xaa/0x110 [ 276.599341] [<ffffffff81203b15>] ? sysfs_write_file+0xe5/0x170 [ 276.616142] [<ffffffff811887b8>] ? vfs_write+0xb8/0x1a0 [ 276.632607] [<ffffffff811890b1>] ? sys_write+0x51/0x90 [ 276.648671] [<ffffffff8100c072>] ? system_call_fastpath+0x16/0x1b [ 276.664756] ---[ end trace 9f5d4fcdd0c3edfc ]--- We forget to clear BCACHE_DEV_UNLINK_DONE flag in bcache_device_attach() function when we attach a backing device first time. After detaching this backing device, this flag will be true and sysfs_remove_link() isn't called in bcache_device_unlink(). Then when we attach this backing device again, sysfs_create_link() will return EEXIST error in bcache_device_link(). So the fix is trival and we clear this flag in bcache_device_link(). Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> Tested-by: Joshua Schmid <jschmid@suse.com> Tested-by: Eric Wheeler <bcache@linux.ewheeler.net> Cc: Kent Overstreet <kmo@daterainc.com> Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -685,6 +685,8 @@ static void bcache_device_link(struct bcache_device *d, struct cache_set *c,
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WARN(sysfs_create_link(&d->kobj, &c->kobj, "cache") ||
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sysfs_create_link(&c->kobj, &d->kobj, d->name),
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"Couldn't create device <-> cache set symlinks");
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clear_bit(BCACHE_DEV_UNLINK_DONE, &d->flags);
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}
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static void bcache_device_detach(struct bcache_device *d)
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