From: Jan Kara Date: Thu, 4 May 2017 07:02:42 +0000 (+0200) Subject: nfs: Fix bdi handling for cloned superblocks X-Git-Tag: v4.12-rc1~77^2~12 X-Git-Url: http://git.samba.org/samba.git/?p=sfrench%2Fcifs-2.6.git;a=commitdiff_plain;h=9052c7cf492d8c52c556f9536c4a9483fbfe4d73 nfs: Fix bdi handling for cloned superblocks 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 [] (unwind_backtrace) from [] (show_stack+0x10/0x14) [] (show_stack) from [] (dump_stack+0x78/0x8c) [] (dump_stack) from [] (__warn+0xe8/0x100) [] (__warn) from [] (warn_slowpath_fmt+0x38/0x48) [] (warn_slowpath_fmt) from [] (sysfs_warn_dup+0x64/0x74) [] (sysfs_warn_dup) from [] (sysfs_create_dir_ns+0x84/0x94) [] (sysfs_create_dir_ns) from [] (kobject_add_internal+0x9c/0x2ec) [] (kobject_add_internal) from [] (kobject_add+0x48/0x98) [] (kobject_add) from [] (device_add+0xe4/0x5a0) [] (device_add) from [] (device_create_groups_vargs+0xac/0xbc) [] (device_create_groups_vargs) from [] (device_create_vargs+0x20/0x28) [] (device_create_vargs) from [] (bdi_register_va+0x44/0xfc) [] (bdi_register_va) from [] (super_setup_bdi_name+0x48/0xa4) [] (super_setup_bdi_name) from [] (nfs_fill_super+0x1a4/0x204) [] (nfs_fill_super) from [] (nfs_fs_mount_common+0x140/0x1e8) [] (nfs_fs_mount_common) from [] (nfs4_remote_mount+0x50/0x58) [] (nfs4_remote_mount) from [] (mount_fs+0x14/0xa4) [] (mount_fs) from [] (vfs_kern_mount+0x54/0x128) [] (vfs_kern_mount) from [] (nfs_do_root_mount+0x80/0xa0) [] (nfs_do_root_mount) from [] (nfs4_try_mount+0x28/0x3c) [] (nfs4_try_mount) from [] (nfs_fs_mount+0x2cc/0x8c4) [] (nfs_fs_mount) from [] (mount_fs+0x14/0xa4) [] (mount_fs) from [] (vfs_kern_mount+0x54/0x128) [] (vfs_kern_mount) from [] (do_mount+0x158/0xc7c) [] (do_mount) from [] (SyS_mount+0x8c/0xb4) [] (SyS_mount) from [] (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: Corentin Labbe Fixes: 0d3b12584972ce5781179ad3f15cca3cdb5cae05 Signed-off-by: Jan Kara Signed-off-by: Jens Axboe --- diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h index 9dc65d7ae754..7b38fedb7e03 100644 --- a/fs/nfs/internal.h +++ b/fs/nfs/internal.h @@ -139,7 +139,7 @@ struct nfs_mount_request { }; struct nfs_mount_info { - int (*fill_super)(struct super_block *, struct nfs_mount_info *); + void (*fill_super)(struct super_block *, struct nfs_mount_info *); int (*set_security)(struct super_block *, struct dentry *, struct nfs_mount_info *); struct nfs_parsed_mount_data *parsed; struct nfs_clone_mount *cloned; @@ -407,7 +407,7 @@ struct dentry *nfs_fs_mount(struct file_system_type *, int, const char *, void * struct dentry * nfs_xdev_mount_common(struct file_system_type *, int, const char *, struct nfs_mount_info *); void nfs_kill_super(struct super_block *); -int nfs_fill_super(struct super_block *, struct nfs_mount_info *); +void nfs_fill_super(struct super_block *, struct nfs_mount_info *); extern struct rpc_stat nfs_rpcstat; @@ -458,7 +458,7 @@ extern void nfs_read_prepare(struct rpc_task *task, void *calldata); extern void nfs_pageio_reset_read_mds(struct nfs_pageio_descriptor *pgio); /* super.c */ -int nfs_clone_super(struct super_block *, struct nfs_mount_info *); +void nfs_clone_super(struct super_block *, struct nfs_mount_info *); void nfs_umount_begin(struct super_block *); int nfs_statfs(struct dentry *, struct kstatfs *); int nfs_show_options(struct seq_file *, struct dentry *); diff --git a/fs/nfs/super.c b/fs/nfs/super.c index dc69314d455e..2f3822a4a7d5 100644 --- a/fs/nfs/super.c +++ b/fs/nfs/super.c @@ -2321,11 +2321,10 @@ inline void nfs_initialise_sb(struct super_block *sb) /* * Finish setting up an NFS2/3 superblock */ -int nfs_fill_super(struct super_block *sb, struct nfs_mount_info *mount_info) +void nfs_fill_super(struct super_block *sb, struct nfs_mount_info *mount_info) { struct nfs_parsed_mount_data *data = mount_info->parsed; struct nfs_server *server = NFS_SB(sb); - int ret; sb->s_blocksize_bits = 0; sb->s_blocksize = 0; @@ -2343,21 +2342,13 @@ int nfs_fill_super(struct super_block *sb, struct nfs_mount_info *mount_info) } nfs_initialise_sb(sb); - - ret = super_setup_bdi_name(sb, "%u:%u", MAJOR(server->s_dev), - MINOR(server->s_dev)); - if (ret) - return ret; - sb->s_bdi->ra_pages = server->rpages * NFS_MAX_READAHEAD; - return 0; - } EXPORT_SYMBOL_GPL(nfs_fill_super); /* * Finish setting up a cloned NFS2/3/4 superblock */ -int nfs_clone_super(struct super_block *sb, struct nfs_mount_info *mount_info) +void nfs_clone_super(struct super_block *sb, struct nfs_mount_info *mount_info) { const struct super_block *old_sb = mount_info->cloned->sb; struct nfs_server *server = NFS_SB(sb); @@ -2377,10 +2368,6 @@ int nfs_clone_super(struct super_block *sb, struct nfs_mount_info *mount_info) } nfs_initialise_sb(sb); - - sb->s_bdi = bdi_get(old_sb->s_bdi); - - return 0; } static int nfs_compare_mount_options(const struct super_block *s, const struct nfs_server *b, int flags) @@ -2600,14 +2587,19 @@ struct dentry *nfs_fs_mount_common(struct nfs_server *server, nfs_free_server(server); server = NULL; } else { + error = super_setup_bdi_name(s, "%u:%u", MAJOR(server->s_dev), + MINOR(server->s_dev)); + if (error) { + mntroot = ERR_PTR(error); + goto error_splat_super; + } + s->s_bdi->ra_pages = server->rpages * NFS_MAX_READAHEAD; server->super = s; } if (!s->s_root) { /* initial superblock/root creation */ - error = mount_info->fill_super(s, mount_info); - if (error) - goto error_splat_super; + mount_info->fill_super(s, mount_info); nfs_get_cache_cookie(s, mount_info->parsed, mount_info->cloned); }