• Jan Kara's avatar
    nfs: Fix bdi handling for cloned superblocks · 9052c7cf
    Jan Kara authored
    In commit 0d3b12584972 "nfs: Convert to separately allocated bdi" I have
    wrongly cloned bdi reference in nfs_clone_super(). Further inspection
    has shown that originally the code was actually allocating a new bdi (in
    ->clone_server callback) which was later registered in
    nfs_fs_mount_common() and used for sb->s_bdi in nfs_initialise_sb().
    This could later result in bdi for the original superblock not getting
    unregistered when that superblock got shutdown (as the cloned sb still
    held bdi reference) and later when a new superblock was created under
    the same anonymous device number, a clash in sysfs has happened on bdi
    registration:
    
    ------------[ cut here ]------------
    WARNING: CPU: 1 PID: 10284 at /linux-next/fs/sysfs/dir.c:31 sysfs_warn_dup+0x64/0x74
    sysfs: cannot create duplicate filename '/devices/virtual/bdi/0:32'
    Modules linked in: axp20x_usb_power gpio_axp209 nvmem_sunxi_sid sun4i_dma sun4i_ss virt_dma
    CPU: 1 PID: 10284 Comm: mount.nfs Not tainted 4.11.0-rc4+ #14
    Hardware name: Allwinner sun7i (A20) Family
    [<c010f19c>] (unwind_backtrace) from [<c010bc74>] (show_stack+0x10/0x14)
    [<c010bc74>] (show_stack) from [<c03c6e24>] (dump_stack+0x78/0x8c)
    [<c03c6e24>] (dump_stack) from [<c0122200>] (__warn+0xe8/0x100)
    [<c0122200>] (__warn) from [<c0122250>] (warn_slowpath_fmt+0x38/0x48)
    [<c0122250>] (warn_slowpath_fmt) from [<c02ac178>] (sysfs_warn_dup+0x64/0x74)
    [<c02ac178>] (sysfs_warn_dup) from [<c02ac254>] (sysfs_create_dir_ns+0x84/0x94)
    [<c02ac254>] (sysfs_create_dir_ns) from [<c03c8b8c>] (kobject_add_internal+0x9c/0x2ec)
    [<c03c8b8c>] (kobject_add_internal) from [<c03c8e24>] (kobject_add+0x48/0x98)
    [<c03c8e24>] (kobject_add) from [<c048d75c>] (device_add+0xe4/0x5a0)
    [<c048d75c>] (device_add) from [<c048ddb4>] (device_create_groups_vargs+0xac/0xbc)
    [<c048ddb4>] (device_create_groups_vargs) from [<c048dde4>] (device_create_vargs+0x20/0x28)
    [<c048dde4>] (device_create_vargs) from [<c02075c8>] (bdi_register_va+0x44/0xfc)
    [<c02075c8>] (bdi_register_va) from [<c023d378>] (super_setup_bdi_name+0x48/0xa4)
    [<c023d378>] (super_setup_bdi_name) from [<c0312ef4>] (nfs_fill_super+0x1a4/0x204)
    [<c0312ef4>] (nfs_fill_super) from [<c03133f0>] (nfs_fs_mount_common+0x140/0x1e8)
    [<c03133f0>] (nfs_fs_mount_common) from [<c03335cc>] (nfs4_remote_mount+0x50/0x58)
    [<c03335cc>] (nfs4_remote_mount) from [<c023ef98>] (mount_fs+0x14/0xa4)
    [<c023ef98>] (mount_fs) from [<c025cba0>] (vfs_kern_mount+0x54/0x128)
    [<c025cba0>] (vfs_kern_mount) from [<c033352c>] (nfs_do_root_mount+0x80/0xa0)
    [<c033352c>] (nfs_do_root_mount) from [<c0333818>] (nfs4_try_mount+0x28/0x3c)
    [<c0333818>] (nfs4_try_mount) from [<c0313874>] (nfs_fs_mount+0x2cc/0x8c4)
    [<c0313874>] (nfs_fs_mount) from [<c023ef98>] (mount_fs+0x14/0xa4)
    [<c023ef98>] (mount_fs) from [<c025cba0>] (vfs_kern_mount+0x54/0x128)
    [<c025cba0>] (vfs_kern_mount) from [<c02600f0>] (do_mount+0x158/0xc7c)
    [<c02600f0>] (do_mount) from [<c0260f98>] (SyS_mount+0x8c/0xb4)
    [<c0260f98>] (SyS_mount) from [<c0107840>] (ret_fast_syscall+0x0/0x3c)
    
    Fix the problem by always creating new bdi for a superblock as we used
    to do.
    Reported-and-tested-by: default avatarCorentin Labbe <clabbe.montjoie@gmail.com>
    Fixes: 0d3b12584972ce5781179ad3f15cca3cdb5cae05
    Signed-off-by: default avatarJan Kara <jack@suse.cz>
    Signed-off-by: default avatarJens Axboe <axboe@fb.com>
    9052c7cf
super.c 74.9 KB