On 24/04/30 01:01PM, Christian Brauner wrote:
> On Mon, Apr 29, 2024 at 12:04:24PM -0500, John Groves wrote:
> > Start building up from the famfs module operations. This commit
> > includes the following:
> >
> > * Register as a file system
> > * Parse mount parameters
> > * Allocate or find (and initialize) a superblock via famfs_get_tree()
> > * Lookup the host dax device, and bail if it's in use (or not dax)
> > * Register as the holder of the dax device if it's available
> > * Add Kconfig and Makefile misc to build famfs
> > * Add FAMFS_SUPER_MAGIC to include/uapi/linux/magic.h
> > * Add export of fs/namei.c:may_open_dev(), which famfs needs to call
> > * Update MAINTAINERS file for the fs/famfs/ path
> >
> > The following exports had to happen to enable famfs:
> >
> > * This uses the new fs/super.c:kill_char_super() - the other kill*super
> > helpers were not quite right.
> > * This uses the dev_dax_iomap export of dax_dev_get()
> >
> > This commit builds but is otherwise too incomplete to run
> >
> > Signed-off-by: John Groves <john@xxxxxxxxxx>
> > ---
> > MAINTAINERS | 1 +
> > fs/Kconfig | 2 +
> > fs/Makefile | 1 +
> > fs/famfs/Kconfig | 10 ++
> > fs/famfs/Makefile | 5 +
> > fs/famfs/famfs_inode.c | 345 +++++++++++++++++++++++++++++++++++++
> > fs/famfs/famfs_internal.h | 36 ++++
> > fs/namei.c | 1 +
> > include/uapi/linux/magic.h | 1 +
> > 9 files changed, 402 insertions(+)
> > create mode 100644 fs/famfs/Kconfig
> > create mode 100644 fs/famfs/Makefile
> > create mode 100644 fs/famfs/famfs_inode.c
> > create mode 100644 fs/famfs/famfs_internal.h
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 3f2d847dcf01..365d678e2f40 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -8188,6 +8188,7 @@ L: linux-cxl@xxxxxxxxxxxxxxx
> > L: linux-fsdevel@xxxxxxxxxxxxxxx
> > S: Supported
> > F: Documentation/filesystems/famfs.rst
> > +F: fs/famfs
> >
> > FANOTIFY
> > M: Jan Kara <jack@xxxxxxx>
> > diff --git a/fs/Kconfig b/fs/Kconfig
> > index a46b0cbc4d8f..53b4629e92a0 100644
> > --- a/fs/Kconfig
> > +++ b/fs/Kconfig
> > @@ -140,6 +140,8 @@ source "fs/autofs/Kconfig"
> > source "fs/fuse/Kconfig"
> > source "fs/overlayfs/Kconfig"
> >
> > +source "fs/famfs/Kconfig"
> > +
> > menu "Caches"
> >
> > source "fs/netfs/Kconfig"
> > diff --git a/fs/Makefile b/fs/Makefile
> > index 6ecc9b0a53f2..3393f399a9e9 100644
> > --- a/fs/Makefile
> > +++ b/fs/Makefile
> > @@ -129,3 +129,4 @@ obj-$(CONFIG_EFIVAR_FS) += efivarfs/
> > obj-$(CONFIG_EROFS_FS) += erofs/
> > obj-$(CONFIG_VBOXSF_FS) += vboxsf/
> > obj-$(CONFIG_ZONEFS_FS) += zonefs/
> > +obj-$(CONFIG_FAMFS) += famfs/
> > diff --git a/fs/famfs/Kconfig b/fs/famfs/Kconfig
> > new file mode 100644
> > index 000000000000..edb8980820f7
> > --- /dev/null
> > +++ b/fs/famfs/Kconfig
> > @@ -0,0 +1,10 @@
> > +
> > +
> > +config FAMFS
> > + tristate "famfs: shared memory file system"
> > + depends on DEV_DAX && FS_DAX && DEV_DAX_IOMAP
> > + help
> > + Support for the famfs file system. Famfs is a dax file system that
> > + can support scale-out shared access to fabric-attached memory
> > + (e.g. CXL shared memory). Famfs is not a general purpose file system;
> > + it is an enabler for data sets in shared memory.
> > diff --git a/fs/famfs/Makefile b/fs/famfs/Makefile
> > new file mode 100644
> > index 000000000000..62230bcd6793
> > --- /dev/null
> > +++ b/fs/famfs/Makefile
> > @@ -0,0 +1,5 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +
> > +obj-$(CONFIG_FAMFS) += famfs.o
> > +
> > +famfs-y := famfs_inode.o
> > diff --git a/fs/famfs/famfs_inode.c b/fs/famfs/famfs_inode.c
> > new file mode 100644
> > index 000000000000..61306240fc0b
> > --- /dev/null
> > +++ b/fs/famfs/famfs_inode.c
> > @@ -0,0 +1,345 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * famfs - dax file system for shared fabric-attached memory
> > + *
> > + * Copyright 2023-2024 Micron Technology, inc
> > + *
> > + * This file system, originally based on ramfs the dax support from xfs,
> > + * is intended to allow multiple host systems to mount a common file system
> > + * view of dax files that map to shared memory.
> > + */
> > +
> > +#include <linux/fs.h>
> > +#include <linux/time.h>
> > +#include <linux/init.h>
> > +#include <linux/string.h>
> > +#include <linux/parser.h>
> > +#include <linux/magic.h>
> > +#include <linux/slab.h>
> > +#include <linux/fs_context.h>
> > +#include <linux/fs_parser.h>
> > +#include <linux/dax.h>
> > +#include <linux/hugetlb.h>
> > +#include <linux/iomap.h>
> > +#include <linux/path.h>
> > +#include <linux/namei.h>
> > +
> > +#include "famfs_internal.h"
> > +
> > +#define FAMFS_DEFAULT_MODE 0755
> > +
> > +static struct inode *famfs_get_inode(struct super_block *sb,
> > + const struct inode *dir,
> > + umode_t mode, dev_t dev)
> > +{
> > + struct inode *inode = new_inode(sb);
> > + struct timespec64 tv;
> > +
> > + if (!inode)
> > + return NULL;
> > +
> > + inode->i_ino = get_next_ino();
> > + inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
> > + inode->i_mapping->a_ops = &ram_aops;
> > + mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
> > + mapping_set_unevictable(inode->i_mapping);
> > + tv = inode_set_ctime_current(inode);
> > + inode_set_mtime_to_ts(inode, tv);
> > + inode_set_atime_to_ts(inode, tv);
> > +
> > + switch (mode & S_IFMT) {
> > + default:
> > + init_special_inode(inode, mode, dev);
> > + break;
> > + case S_IFREG:
> > + inode->i_op = NULL /* famfs_file_inode_operations */;
> > + inode->i_fop = NULL /* &famfs_file_operations */;
> > + break;
> > + case S_IFDIR:
> > + inode->i_op = NULL /* famfs_dir_inode_operations */;
> > + inode->i_fop = &simple_dir_operations;
> > +
> > + /* Directory inodes start off with i_nlink == 2 (for ".") */
> > + inc_nlink(inode);
> > + break;
> > + case S_IFLNK:
> > + inode->i_op = &page_symlink_inode_operations;
> > + inode_nohighmem(inode);
> > + break;
> > + }
> > + return inode;
> > +}
> > +
> > +/*
> > + * famfs dax_operations (for char dax)
> > + */
> > +static int
> > +famfs_dax_notify_failure(struct dax_device *dax_dev, u64 offset,
> > + u64 len, int mf_flags)
> > +{
> > + struct super_block *sb = dax_holder(dax_dev);
> > + struct famfs_fs_info *fsi = sb->s_fs_info;
> > +
> > + pr_err("%s: rootdev=%s offset=%lld len=%llu flags=%x\n", __func__,
> > + fsi->rootdev, offset, len, mf_flags);
> > +
> > + return 0;
> > +}
> > +
> > +static const struct dax_holder_operations famfs_dax_holder_ops = {
> > + .notify_failure = famfs_dax_notify_failure,
> > +};
> > +
> > +/*****************************************************************************
> > + * fs_context_operations
> > + */
> > +
> > +static int
> > +famfs_fill_super(struct super_block *sb, struct fs_context *fc)
> > +{
> > + int rc = 0;
> > +
> > + sb->s_maxbytes = MAX_LFS_FILESIZE;
> > + sb->s_blocksize = PAGE_SIZE;
> > + sb->s_blocksize_bits = PAGE_SHIFT;
> > + sb->s_magic = FAMFS_SUPER_MAGIC;
> > + sb->s_op = NULL /* famfs_super_ops */;
> > + sb->s_time_gran = 1;
> > +
> > + return rc;
> > +}
> > +
> > +static int
> > +lookup_daxdev(const char *pathname, dev_t *devno)
> > +{
> > + struct inode *inode;
> > + struct path path;
> > + int err;
> > +
> > + if (!pathname || !*pathname)
> > + return -EINVAL;
> > +
> > + err = kern_path(pathname, LOOKUP_FOLLOW, &path);
> > + if (err)
> > + return err;
> > +
> > + inode = d_backing_inode(path.dentry);
> > + if (!S_ISCHR(inode->i_mode)) {
> > + err = -EINVAL;
> > + goto out_path_put;
> > + }
> > +
> > + if (!may_open_dev(&path)) { /* had to export this */
> > + err = -EACCES;
> > + goto out_path_put;
> > + }
> > +
> > + /* if it's dax, i_rdev is struct dax_device */
> > + *devno = inode->i_rdev;
> > +
> > +out_path_put:
> > + path_put(&path);
> > + return err;
> > +}
> > +
> > +static int
> > +famfs_get_tree(struct fs_context *fc)
> > +{
> > + struct famfs_fs_info *fsi = fc->s_fs_info;
> > + struct dax_device *dax_devp;
> > + struct super_block *sb;
> > + struct inode *inode;
> > + dev_t daxdevno;
> > + int err;
> > +
> > + /* TODO: clean up chatty messages */
> > +
> > + err = lookup_daxdev(fc->source, &daxdevno);
> > + if (err)
> > + return err;
> > +
> > + fsi->daxdevno = daxdevno;
> > +
> > + /* This will set sb->s_dev=daxdevno */
> > + sb = sget_dev(fc, daxdevno);
>
> This will open the dax device as a block device. However, nothing in
> your ->kill_sb method or kill_char_super() closes it again. So you're
> leaking block device references and leaving unitialized memory around as
> you've claimed that device but never ended your claim.
>
> > + if (IS_ERR(sb)) {
> > + pr_err("%s: sget_dev error\n", __func__);
> > + return PTR_ERR(sb);
> > + }
> > +
> > + if (sb->s_root) {
> > + pr_info("%s: found a matching suerblock for %s\n",
> > + __func__, fc->source);
> > +
> > + /* We don't expect to find a match by dev_t; if we do, it must
> > + * already be mounted, so we bail
> > + */
> > + err = -EBUSY;
> > + goto deactivate_out;
> > + } else {
> > + pr_info("%s: initializing new superblock for %s\n",
> > + __func__, fc->source);
> > + err = famfs_fill_super(sb, fc);
> > + if (err)
> > + goto deactivate_out;
> > + }
> > +
> > + /* This will fail if it's not a dax device */
> > + dax_devp = dax_dev_get(daxdevno);
> > + if (!dax_devp) {
> > + pr_warn("%s: device %s not found or not dax\n",
> > + __func__, fc->source);
> > + err = -ENODEV;
> > + goto deactivate_out;
> > + }
> > +
> > + err = fs_dax_get(dax_devp, sb, &famfs_dax_holder_ops);
> > + if (err) {
> > + pr_err("%s: fs_dax_get(%lld) failed\n", __func__, (u64)daxdevno);
> > + err = -EBUSY;
> > + goto deactivate_out;
> > + }
> > + fsi->dax_devp = dax_devp;
> > +
> > + inode = famfs_get_inode(sb, NULL, S_IFDIR | fsi->mount_opts.mode, 0);
> > + sb->s_root = d_make_root(inode);
> > + if (!sb->s_root) {
> > + pr_err("%s: d_make_root() failed\n", __func__);
> > + err = -ENOMEM;
> > + fs_put_dax(fsi->dax_devp, sb);
> > + goto deactivate_out;
> > + }
> > +
> > + sb->s_flags |= SB_ACTIVE;
> > +
> > + WARN_ON(fc->root);
> > + fc->root = dget(sb->s_root);
> > + return err;
> > +
> > +deactivate_out:
> > + pr_debug("%s: deactivating sb=%llx\n", __func__, (u64)sb);
> > + deactivate_locked_super(sb);
> > + return err;
> > +}
> > +
> > +/*****************************************************************************/
> > +
> > +enum famfs_param {
> > + Opt_mode,
> > + Opt_dax,
> > +};
> > +
> > +const struct fs_parameter_spec famfs_fs_parameters[] = {
> > + fsparam_u32oct("mode", Opt_mode),
> > + fsparam_string("dax", Opt_dax),
> > + {}
> > +};
> > +
> > +static int famfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
> > +{
> > + struct famfs_fs_info *fsi = fc->s_fs_info;
> > + struct fs_parse_result result;
> > + int opt;
> > +
> > + opt = fs_parse(fc, famfs_fs_parameters, param, &result);
> > + if (opt == -ENOPARAM) {
> > + opt = vfs_parse_fs_param_source(fc, param);
> > + if (opt != -ENOPARAM)
> > + return opt;
>
> This shouldn't be needed. The VFS will handle all that for you.
>
> > +
> > + return 0;
> > + }
> > + if (opt < 0)
> > + return opt;
> > +
> > + switch (opt) {
> > + case Opt_mode:
> > + fsi->mount_opts.mode = result.uint_32 & S_IALLUGO;
> > + break;
> > + case Opt_dax:
> > + if (strcmp(param->string, "always"))
> > + pr_notice("%s: invalid dax mode %s\n",
> > + __func__, param->string);
> > + break;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static void famfs_free_fc(struct fs_context *fc)
> > +{
> > + struct famfs_fs_info *fsi = fc->s_fs_info;
> > +
> > + if (fsi && fsi->rootdev)
> > + kfree(fsi->rootdev);
>
> Dead code since rootdev is unused an unset?
>
> > +
> > + kfree(fsi);
> > +}
> > +
> > +static const struct fs_context_operations famfs_context_ops = {
> > + .free = famfs_free_fc,
> > + .parse_param = famfs_parse_param,
> > + .get_tree = famfs_get_tree,
> > +};
> > +
> > +static int famfs_init_fs_context(struct fs_context *fc)
> > +{
> > + struct famfs_fs_info *fsi;
> > +
> > + fsi = kzalloc(sizeof(*fsi), GFP_KERNEL);
> > + if (!fsi)
> > + return -ENOMEM;
> > +
> > + fsi->mount_opts.mode = FAMFS_DEFAULT_MODE;
> > + fc->s_fs_info = fsi;
> > + fc->ops = &famfs_context_ops;
> > + return 0;
> > +}
> > +
> > +static void famfs_kill_sb(struct super_block *sb)
> > +{
> > + struct famfs_fs_info *fsi = sb->s_fs_info;
> > +
> > + if (fsi->dax_devp)
> > + fs_put_dax(fsi->dax_devp, sb);
> > + if (fsi && fsi->rootdev)
> > + kfree(fsi->rootdev);
> > + kfree(fsi);
> > + sb->s_fs_info = NULL;
> > +
> > + kill_char_super(sb); /* new */
> > +}
>
> Can likely just be
>
> static void famfs_kill_sb(struct super_block *sb)
> {
> struct famfs_fs_info *fsi = sb->s_fs_info;
>
> generic_shutdown_super(sb);
>
> if (sb->s_bdev_file)
> bdev_fput(sb->s_bdev_file);
>
> if (fsi->dax_devp)
> fs_put_dax(fsi->dax_devp, sb);
>
> kfree(fsi);
> }
>
> and then you don't need any custom helpers at all.
I replaced famfs_kill_sb() with this function. On [the first] umount, I
get one of these dentry bugs for each file in the file system:
May 03 07:27:03 f39-dev1 kernel: ------------[ cut here ]------------
May 03 07:27:03 f39-dev1 kernel: BUG: Dentry 0000000033362594{i=217d,n=smoke_loop4.log} still in use (1) [unmount of famfs famfs]
May 03 07:27:03 f39-dev1 kernel: WARNING: CPU: 0 PID: 1138 at fs/dcache.c:1524 umount_check+0x56/0x70
May 03 07:27:03 f39-dev1 kernel: Modules linked in: famfs rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace netfs qrtr rfkill intel_rapl_msr sunrpc snd_hda_codec_generic intel_rapl_common snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi kvm_intel snd_hda_codec kmem snd_hda_core iTCO_wdt intel_pmc_bxt snd_hwdep device_dax iTCO_vendor_support kvm snd_seq snd_seq_device rapl dax_hmem cxl_acpi snd_pcm cxl_core i2c_i801 snd_timer einj pcspkr i2c_smbus snd lpc_ich soundcore virtio_balloon joydev vfat fat fuse loop zram xfs crct10dif_pclmul crc32_pclmul crc32c_intel polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 sha256_ssse3 sha1_ssse3 virtio_blk virtio_console virtio_gpu virtio_net net_failover virtio_dma_buf failover serio_raw scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_multipath qemu_fw_cfg
May 03 07:27:03 f39-dev1 kernel: CPU: 0 PID: 1138 Comm: umount Tainted: G W 6.9.0-rc5+ #266
May 03 07:27:03 f39-dev1 kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230301gitf80f052277c8-26.fc38 03/01/2023
May 03 07:27:03 f39-dev1 kernel: RIP: 0010:umount_check+0x56/0x70
May 03 07:27:03 f39-dev1 kernel: Code: 03 00 00 48 8b 40 28 48 89 e5 4c 8b 08 48 8b 46 30 48 85 c0 74 04 48 8b 50 40 51 48 c7 c7 b0 a6 ae 82 48 89 f1 e8 ba 56 c4 ff <0f> 0b 58 31 c0 c9 c3 cc cc cc cc 41 83 f8 01 75 ba eb a8 0f 1f 80
May 03 07:27:03 f39-dev1 kernel: RSP: 0018:ffffc90000717bd0 EFLAGS: 00010282
May 03 07:27:03 f39-dev1 kernel: RAX: 0000000000000000 RBX: 0000000000000f34 RCX: 0000000000000000
May 03 07:27:03 f39-dev1 kernel: RDX: 0000000000000004 RSI: ffffffff82b1c111 RDI: 00000000ffffffff
May 03 07:27:03 f39-dev1 kernel: RBP: ffffc90000717bd8 R08: 0000000000000000 R09: 0000000000000003
May 03 07:27:03 f39-dev1 kernel: R10: ffffc90000717a20 R11: ffffffff82f3c3a8 R12: ffff8881007be840
May 03 07:27:03 f39-dev1 kernel: R13: ffffffff814d8ae0 R14: ffff8881007be8a0 R15: ffff88810d82ab40
May 03 07:27:03 f39-dev1 kernel: FS: 00007f3163f71800(0000) GS:ffff88886fc00000(0000) knlGS:0000000000000000
May 03 07:27:03 f39-dev1 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 03 07:27:03 f39-dev1 kernel: CR2: 00007fff84673f78 CR3: 000000010c338002 CR4: 0000000000170ef0
May 03 07:27:03 f39-dev1 kernel: Call Trace:
May 03 07:27:03 f39-dev1 kernel: <TASK>
May 03 07:27:03 f39-dev1 kernel: ? show_regs+0x64/0x70
May 03 07:27:03 f39-dev1 kernel: ? __warn+0x88/0x130
May 03 07:27:03 f39-dev1 kernel: ? umount_check+0x56/0x70
May 03 07:27:03 f39-dev1 kernel: ? report_bug+0x192/0x1c0
May 03 07:27:03 f39-dev1 kernel: ? handle_bug+0x44/0x90
May 03 07:27:03 f39-dev1 kernel: ? exc_invalid_op+0x18/0x70
May 03 07:27:03 f39-dev1 kernel: ? asm_exc_invalid_op+0x1b/0x20
May 03 07:27:03 f39-dev1 kernel: ? __pfx_umount_check+0x10/0x10
May 03 07:27:03 f39-dev1 kernel: ? umount_check+0x56/0x70
May 03 07:27:03 f39-dev1 kernel: d_walk+0xc3/0x280
May 03 07:27:03 f39-dev1 kernel: shrink_dcache_for_umount+0x4e/0x130
May 03 07:27:03 f39-dev1 kernel: generic_shutdown_super+0x1f/0x120
May 03 07:27:03 f39-dev1 kernel: famfs_kill_sb+0x1b/0x70 [famfs]
May 03 07:27:03 f39-dev1 kernel: deactivate_locked_super+0x35/0xb0
May 03 07:27:03 f39-dev1 kernel: deactivate_super+0x40/0x50
May 03 07:27:03 f39-dev1 kernel: cleanup_mnt+0xc3/0x160
May 03 07:27:03 f39-dev1 kernel: __cleanup_mnt+0x12/0x20
May 03 07:27:03 f39-dev1 kernel: task_work_run+0x60/0x90
May 03 07:27:03 f39-dev1 kernel: syscall_exit_to_user_mode+0x21a/0x220
May 03 07:27:03 f39-dev1 kernel: do_syscall_64+0x8d/0x180
May 03 07:27:03 f39-dev1 kernel: ? mntput+0x24/0x40
May 03 07:27:03 f39-dev1 kernel: ? path_put+0x1e/0x30
May 03 07:27:03 f39-dev1 kernel: ? do_faccessat+0x1b8/0x2e0
May 03 07:27:03 f39-dev1 kernel: ? syscall_exit_to_user_mode+0x7c/0x220
May 03 07:27:03 f39-dev1 kernel: ? do_syscall_64+0x8d/0x180
May 03 07:27:03 f39-dev1 kernel: ? putname+0x55/0x70
May 03 07:27:03 f39-dev1 kernel: ? syscall_exit_to_user_mode+0x7c/0x220
May 03 07:27:03 f39-dev1 kernel: ? do_syscall_64+0x8d/0x180
May 03 07:27:03 f39-dev1 kernel: ? do_user_addr_fault+0x315/0x6e0
May 03 07:27:03 f39-dev1 kernel: ? irqentry_exit_to_user_mode+0x71/0x220
May 03 07:27:03 f39-dev1 kernel: ? irqentry_exit+0x3b/0x50
May 03 07:27:03 f39-dev1 kernel: ? exc_page_fault+0x90/0x190
May 03 07:27:03 f39-dev1 kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e
May 03 07:27:03 f39-dev1 kernel: RIP: 0033:0x7f316419041b
May 03 07:27:03 f39-dev1 kernel: Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 e1 19 0c 00 f7 d8
May 03 07:27:03 f39-dev1 kernel: RSP: 002b:00007fff84675728 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
May 03 07:27:03 f39-dev1 kernel: RAX: 0000000000000000 RBX: 00005648cab2eb90 RCX: 00007f316419041b
May 03 07:27:03 f39-dev1 kernel: RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00005648cab33ba0
May 03 07:27:03 f39-dev1 kernel: RBP: 00007fff84675800 R08: 0000000000000020 R09: 0000000000000001
May 03 07:27:03 f39-dev1 kernel: R10: 0000000000000004 R11: 0000000000000246 R12: 00005648cab2ec90
May 03 07:27:03 f39-dev1 kernel: R13: 0000000000000000 R14: 00005648cab33ba0 R15: 00005648cab2efa0
May 03 07:27:03 f39-dev1 kernel: </TASK>
May 03 07:27:03 f39-dev1 kernel: ---[ end trace 0000000000000000 ]---
After one of the above for every file:
May 03 07:27:03 f39-dev1 kernel: VFS: Busy inodes after unmount of famfs (famfs)
May 03 07:27:03 f39-dev1 kernel: ------------[ cut here ]------------
May 03 07:27:03 f39-dev1 kernel: kernel BUG at fs/super.c:649!
May 03 07:27:03 f39-dev1 kernel: invalid opcode: 0000 [#1] PREEMPT SMP PTI
May 03 07:27:03 f39-dev1 kernel: CPU: 3 PID: 1138 Comm: umount Tainted: G W 6.9.0-rc5+ #266
May 03 07:27:03 f39-dev1 kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS edk2-20230301gitf80f052277c8-26.fc38 03/01/2023
May 03 07:27:03 f39-dev1 kernel: RIP: 0010:generic_shutdown_super+0x112/0x120
May 03 07:27:03 f39-dev1 kernel: Code: cc cc e8 e1 4f f0 ff 48 8b bb 00 01 00 00 eb d9 48 8b 43 28 48 8d b3 c0 03 00 00 48 c7 c7 c0 98 ae 82 48 8b 10 e8 5e 2d d0 ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90
May 03 07:27:03 f39-dev1 kernel: RSP: 0018:ffffc90000717c70 EFLAGS: 00010246
May 03 07:27:03 f39-dev1 kernel: RAX: 000000000000002f RBX: ffff8881215d5000 RCX: 0000000000000000
May 03 07:27:03 f39-dev1 kernel: RDX: 0000000000000000 RSI: ffffffff82b1c111 RDI: 00000000ffffffff
May 03 07:27:03 f39-dev1 kernel: RBP: ffffc90000717c80 R08: 0000000000000000 R09: 0000000000000003
May 03 07:27:03 f39-dev1 kernel: R10: ffffc90000717ad8 R11: ffffffff82f3c3a8 R12: ffffffffa0cf4380
May 03 07:27:03 f39-dev1 kernel: R13: ffff888124ed359c R14: 0000000000000000 R15: 0000000000000000
May 03 07:27:03 f39-dev1 kernel: FS: 00007f3163f71800(0000) GS:ffff88886fd80000(0000) knlGS:0000000000000000
May 03 07:27:03 f39-dev1 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 03 07:27:03 f39-dev1 kernel: CR2: 000055fd5fc6a370 CR3: 000000010c338003 CR4: 0000000000170ef0
May 03 07:27:03 f39-dev1 kernel: Call Trace:
May 03 07:27:03 f39-dev1 kernel: <TASK>
May 03 07:27:03 f39-dev1 kernel: ? show_regs+0x64/0x70
May 03 07:27:03 f39-dev1 kernel: ? die+0x37/0x90
May 03 07:27:03 f39-dev1 kernel: ? do_trap+0xca/0xe0
May 03 07:27:03 f39-dev1 kernel: ? do_error_trap+0x73/0xa0
May 03 07:27:03 f39-dev1 kernel: ? generic_shutdown_super+0x112/0x120
May 03 07:27:03 f39-dev1 kernel: ? exc_invalid_op+0x52/0x70
May 03 07:27:03 f39-dev1 kernel: ? generic_shutdown_super+0x112/0x120
May 03 07:27:03 f39-dev1 kernel: ? asm_exc_invalid_op+0x1b/0x20
May 03 07:27:03 f39-dev1 kernel: ? generic_shutdown_super+0x112/0x120
May 03 07:27:03 f39-dev1 kernel: famfs_kill_sb+0x1b/0x70 [famfs]
May 03 07:27:03 f39-dev1 kernel: deactivate_locked_super+0x35/0xb0
May 03 07:27:03 f39-dev1 kernel: deactivate_super+0x40/0x50
May 03 07:27:03 f39-dev1 kernel: cleanup_mnt+0xc3/0x160
May 03 07:27:03 f39-dev1 kernel: __cleanup_mnt+0x12/0x20
May 03 07:27:03 f39-dev1 kernel: task_work_run+0x60/0x90
May 03 07:27:03 f39-dev1 kernel: syscall_exit_to_user_mode+0x21a/0x220
May 03 07:27:03 f39-dev1 kernel: do_syscall_64+0x8d/0x180
May 03 07:27:03 f39-dev1 kernel: ? mntput+0x24/0x40
May 03 07:27:03 f39-dev1 kernel: ? path_put+0x1e/0x30
May 03 07:27:03 f39-dev1 kernel: ? do_faccessat+0x1b8/0x2e0
May 03 07:27:03 f39-dev1 kernel: ? syscall_exit_to_user_mode+0x7c/0x220
May 03 07:27:03 f39-dev1 kernel: ? do_syscall_64+0x8d/0x180
May 03 07:27:03 f39-dev1 kernel: ? putname+0x55/0x70
May 03 07:27:03 f39-dev1 kernel: ? syscall_exit_to_user_mode+0x7c/0x220
May 03 07:27:03 f39-dev1 kernel: ? do_syscall_64+0x8d/0x180
May 03 07:27:03 f39-dev1 kernel: ? do_user_addr_fault+0x315/0x6e0
May 03 07:27:03 f39-dev1 kernel: ? irqentry_exit_to_user_mode+0x71/0x220
May 03 07:27:03 f39-dev1 kernel: ? irqentry_exit+0x3b/0x50
May 03 07:27:03 f39-dev1 kernel: ? exc_page_fault+0x90/0x190
May 03 07:27:03 f39-dev1 kernel: entry_SYSCALL_64_after_hwframe+0x76/0x7e
May 03 07:27:03 f39-dev1 kernel: RIP: 0033:0x7f316419041b
May 03 07:27:03 f39-dev1 kernel: Code: c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 f3 0f 1e fa 31 f6 e9 05 00 00 00 0f 1f 44 00 00 f3 0f 1e fa b8 a6 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 05 c3 0f 1f 40 00 48 8b 15 e1 19 0c 00 f7 d8
May 03 07:27:03 f39-dev1 kernel: RSP: 002b:00007fff84675728 EFLAGS: 00000246 ORIG_RAX: 00000000000000a6
May 03 07:27:03 f39-dev1 kernel: RAX: 0000000000000000 RBX: 00005648cab2eb90 RCX: 00007f316419041b
May 03 07:27:03 f39-dev1 kernel: RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00005648cab33ba0
May 03 07:27:03 f39-dev1 kernel: RBP: 00007fff84675800 R08: 0000000000000020 R09: 0000000000000001
May 03 07:27:03 f39-dev1 kernel: R10: 0000000000000004 R11: 0000000000000246 R12: 00005648cab2ec90
May 03 07:27:03 f39-dev1 kernel: R13: 0000000000000000 R14: 00005648cab33ba0 R15: 00005648cab2efa0
May 03 07:27:03 f39-dev1 kernel: </TASK>
May 03 07:27:03 f39-dev1 kernel: Modules linked in: famfs rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace netfs qrtr rfkill intel_rapl_msr sunrpc snd_hda_codec_generic intel_rapl_common snd_hda_intel snd_intel_dspcfg snd_intel_sdw_acpi kvm_intel snd_hda_codec kmem snd_hda_core iTCO_wdt intel_pmc_bxt snd_hwdep device_dax iTCO_vendor_support kvm snd_seq snd_seq_device rapl dax_hmem cxl_acpi snd_pcm cxl_core i2c_i801 snd_timer einj pcspkr i2c_smbus snd lpc_ich soundcore virtio_balloon joydev vfat fat fuse loop zram xfs crct10dif_pclmul crc32_pclmul crc32c_intel polyval_clmulni polyval_generic ghash_clmulni_intel sha512_ssse3 sha256_ssse3 sha1_ssse3 virtio_blk virtio_console virtio_gpu virtio_net net_failover virtio_dma_buf failover serio_raw scsi_dh_rdac scsi_dh_emc scsi_dh_alua dm_multipath qemu_fw_cfg
May 03 07:27:03 f39-dev1 kernel: ---[ end trace 0000000000000000 ]---
May 03 07:27:03 f39-dev1 kernel: RIP: 0010:generic_shutdown_super+0x112/0x120
May 03 07:27:03 f39-dev1 kernel: Code: cc cc e8 e1 4f f0 ff 48 8b bb 00 01 00 00 eb d9 48 8b 43 28 48 8d b3 c0 03 00 00 48 c7 c7 c0 98 ae 82 48 8b 10 e8 5e 2d d0 ff <0f> 0b 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90
May 03 07:27:03 f39-dev1 kernel: RSP: 0018:ffffc90000717c70 EFLAGS: 00010246
May 03 07:27:03 f39-dev1 kernel: RAX: 000000000000002f RBX: ffff8881215d5000 RCX: 0000000000000000
May 03 07:27:03 f39-dev1 kernel: RDX: 0000000000000000 RSI: ffffffff82b1c111 RDI: 00000000ffffffff
May 03 07:27:03 f39-dev1 kernel: RBP: ffffc90000717c80 R08: 0000000000000000 R09: 0000000000000003
May 03 07:27:03 f39-dev1 kernel: R10: ffffc90000717ad8 R11: ffffffff82f3c3a8 R12: ffffffffa0cf4380
May 03 07:27:03 f39-dev1 kernel: R13: ffff888124ed359c R14: 0000000000000000 R15: 0000000000000000
May 03 07:27:03 f39-dev1 kernel: FS: 00007f3163f71800(0000) GS:ffff88886fd80000(0000) knlGS:0000000000000000
May 03 07:27:03 f39-dev1 kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
May 03 07:27:03 f39-dev1 kernel: CR2: 000055fd5fc6a370 CR3: 000000010c338003 CR4: 0000000000170ef0
These BUG dumps are familiar; famfs_kill_sb()/kill_char_sb() in this
patch set are clean in this regard. (I'm not saying they're "right", but
clean). But to be clear, blowing away the dentries is appropriate in the
famfs case.
An important thing, I think, is that instantiation of famfs file
(which happens when user space plays the log) looks a lot like creating
ramfs files - except that after an empty ramfs-like file is created,
an ioctl is called to "tell the file where its backing memory is".
And famfs does not persist metadata changes, which is a feature and
not a bug...
I think the d_genocide() call is what cleans up the dentry cache with
famfs_kill_sb() from the patch (which calls the new kill_char_super()).
Thanks for any suggestions,
John
