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Date: Wed, 6 Jun 2018 20:58:56 -0500
From: Goldwyn Rodrigues <rgoldwyn@...e.de>
To: David Howells <dhowells@...hat.com>, viro@...iv.linux.org.uk
Cc: linux-fsdevel@...r.kernel.org, linux-afs@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 26/32] afs: Use fs_context to pass parameters over
automount [ver #8]
On 05/24/2018 07:08 PM, David Howells wrote:
> Alter the AFS automounting code to create and modify an fs_context struct
> when parameterising a new mount triggered by an AFS mountpoint rather than
> constructing device name and option strings.
>
> Also remove the cell=, vol= and rwpath options as they are then redundant.
> The reason they existed is because the 'device name' may be derived
> literally from a mountpoint object in the filesystem, so default cell and
> parent-type information needed to be passed in by some other method from
> the automount routines. The vol= option didn't end up being used.
>
> Signed-off-by: David Howells <dhowells@...hat.com>
> cc: Eric W. Biederman <ebiederm@...hat.com>
> ---
>
> fs/afs/internal.h | 1
> fs/afs/mntpt.c | 148 +++++++++++++++++++++++++++--------------------------
> fs/afs/super.c | 43 +--------------
> 3 files changed, 79 insertions(+), 113 deletions(-)
>
> diff --git a/fs/afs/internal.h b/fs/afs/internal.h
> index eb6e75e00181..90af5001f8c8 100644
> --- a/fs/afs/internal.h
> +++ b/fs/afs/internal.h
> @@ -35,7 +35,6 @@ struct pagevec;
> struct afs_call;
>
> struct afs_fs_context {
> - bool rwpath; /* T if the parent should be considered R/W */
> bool force; /* T to force cell type */
> bool autocell; /* T if set auto mount operation */
> bool dyn_root; /* T if dynamic root */
> diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
> index c45aa1776591..fc383d727552 100644
> --- a/fs/afs/mntpt.c
> +++ b/fs/afs/mntpt.c
> @@ -47,6 +47,8 @@ static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
>
> static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
>
> +static const char afs_root_volume[] = "root.cell";
> +
> /*
> * no valid lookup procedure on this sort of dir
> */
> @@ -68,107 +70,107 @@ static int afs_mntpt_open(struct inode *inode, struct file *file)
> }
>
> /*
> - * create a vfsmount to be automounted
> + * Set the parameters for the proposed superblock.
> */
> -static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
> +static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
> {
> - struct afs_super_info *as;
> - struct vfsmount *mnt;
> - struct afs_vnode *vnode;
> - struct page *page;
> - char *devname, *options;
> - bool rwpath = false;
> + struct afs_fs_context *ctx = fc->fs_private;
> + struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
> + struct afs_cell *cell;
> + const char *p;
> int ret;
>
> - _enter("{%pd}", mntpt);
> -
> - BUG_ON(!d_inode(mntpt));
> -
> - ret = -ENOMEM;
> - devname = (char *) get_zeroed_page(GFP_KERNEL);
> - if (!devname)
> - goto error_no_devname;
> -
> - options = (char *) get_zeroed_page(GFP_KERNEL);
> - if (!options)
> - goto error_no_options;
> -
> - vnode = AFS_FS_I(d_inode(mntpt));
> if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
> /* if the directory is a pseudo directory, use the d_name */
> - static const char afs_root_cell[] = ":root.cell.";
> unsigned size = mntpt->d_name.len;
>
> - ret = -ENOENT;
> - if (size < 2 || size > AFS_MAXCELLNAME)
> - goto error_no_page;
> + if (size < 2)
> + return -ENOENT;
>
> + p = mntpt->d_name.name;
> if (mntpt->d_name.name[0] == '.') {
> - devname[0] = '%';
> - memcpy(devname + 1, mntpt->d_name.name + 1, size - 1);
> - memcpy(devname + size, afs_root_cell,
> - sizeof(afs_root_cell));
> - rwpath = true;
> - } else {
> - devname[0] = '#';
> - memcpy(devname + 1, mntpt->d_name.name, size);
> - memcpy(devname + size + 1, afs_root_cell,
> - sizeof(afs_root_cell));
> + size--;
> + p++;
> + ctx->type = AFSVL_RWVOL;
> + ctx->force = true;
> + }
> + if (size > AFS_MAXCELLNAME)
> + return -ENAMETOOLONG;
> +
> + cell = afs_lookup_cell(ctx->net, p, size, NULL, false);
> + if (IS_ERR(cell)) {
> + pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
> + return PTR_ERR(cell);
> }
> + afs_put_cell(ctx->net, ctx->cell);
> + ctx->cell = cell;
> +
> + ctx->volname = afs_root_volume;
> + ctx->volnamesz = sizeof(afs_root_volume) - 1;
> } else {
> /* read the contents of the AFS special symlink */
> + struct page *page;
> loff_t size = i_size_read(d_inode(mntpt));
> char *buf;
>
> - ret = -EINVAL;
> if (size > PAGE_SIZE - 1)
> - goto error_no_page;
> + return -EINVAL;
>
> page = read_mapping_page(d_inode(mntpt)->i_mapping, 0, NULL);
> - if (IS_ERR(page)) {
> - ret = PTR_ERR(page);
> - goto error_no_page;
> - }
> + if (IS_ERR(page))
> + return PTR_ERR(page);
>
> - ret = -EIO;
> - if (PageError(page))
> - goto error;
> + if (PageError(page)) {
> + put_page(page);
> + return -EIO;
> + }
>
> - buf = kmap_atomic(page);
> - memcpy(devname, buf, size);
> - kunmap_atomic(buf);
> + buf = kmap(page);
> + ret = vfs_set_fs_source(fc, buf, size);
> + kunmap(page);
> put_page(page);
> - page = NULL;
> + if (ret < 0)
> + return ret;
> }
>
> - /* work out what options we want */
> - as = AFS_FS_S(mntpt->d_sb);
> - if (as->cell) {
> - memcpy(options, "cell=", 5);
> - strcpy(options + 5, as->cell->name);
> - if ((as->volume && as->volume->type == AFSVL_RWVOL) || rwpath)
> - strcat(options, ",rwpath");
> - }
> + return 0;
> +}
>
> - /* try and do the mount */
> - _debug("--- attempting mount %s -o %s ---", devname, options);
> - mnt = vfs_submount(mntpt, &afs_fs_type, devname,
> - options, strlen(options) + 1);
> - _debug("--- mount result %p ---", mnt);
> +/*
> + * create a vfsmount to be automounted
> + */
> +static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
> +{
> + struct fs_context *fc;
> + struct vfsmount *mnt;
> + int ret;
> +
> + BUG_ON(!d_inode(mntpt));
> +
> + fc = vfs_new_fs_context(&afs_fs_type, mntpt, 0,
> + FS_CONTEXT_FOR_SUBMOUNT);
> + if (IS_ERR(fc))
> + return ERR_CAST(fc);
> +
> + ret = afs_mntpt_set_params(fc, mntpt);
> + if (ret < 0)
> + goto error_fc;
> +
> + ret = vfs_get_tree(fc);
> + if (ret < 0)
> + goto error_fc;
> +
> + mnt = vfs_create_mount(fc, 0);
> + if (IS_ERR(mnt)) {
> + ret = PTR_ERR(mnt);
> + goto error_fc;
> + }
>
> - free_page((unsigned long) devname);
> - free_page((unsigned long) options);
> - _leave(" = %p", mnt);
> + put_fs_context(fc);
> return mnt;
>
Why are you performing a put_fs_context(fc) in the success code path? Do
we not need a reference of fc anymore?
> -error:
> - put_page(page);
> -error_no_page:
> - free_page((unsigned long) options);
> -error_no_options:
> - free_page((unsigned long) devname);
> -error_no_devname:
> - _leave(" = %d", ret);
> +error_fc:
> + put_fs_context(fc);
> return ERR_PTR(ret);
> }
>
--
Goldwyn
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