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Message-ID: <20090716192755.GE2495@fieldses.org>
Date: Thu, 16 Jul 2009 15:27:55 -0400
From: "J. Bruce Fields" <bfields@...ldses.org>
To: Sage Weil <sage@...dream.net>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 16/20] ceph: nfs re-export support
On Wed, Jul 15, 2009 at 02:24:46PM -0700, Sage Weil wrote:
> Basic NFS re-export support is included. This mostly works. However,
> Ceph's MDS design precludes the ability to generate a (small)
> filehandle that will be valid forever, so this is of limited utility.
Is there any hope of fixing that?
--b.
>
> Signed-off-by: Sage Weil <sage@...dream.net>
> ---
> fs/ceph/export.c | 155 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 155 insertions(+), 0 deletions(-)
> create mode 100644 fs/ceph/export.c
>
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> new file mode 100644
> index 0000000..6ec1629
> --- /dev/null
> +++ b/fs/ceph/export.c
> @@ -0,0 +1,155 @@
> +#include <linux/exportfs.h>
> +#include <asm/unaligned.h>
> +
> +#include "super.h"
> +#include "ceph_debug.h"
> +
> +int ceph_debug_export __read_mostly = -1;
> +#define DOUT_MASK DOUT_MASK_EXPORT
> +#define DOUT_VAR ceph_debug_export
> +
> +/*
> + * fh is N tuples of
> + * <ino, parent's d_name.hash>
> + *
> + * This is only a semi-reliable strategy. The fundamental issue is
> + * that ceph doesn't not have a way to locate an arbitrary inode by
> + * ino. Keeping a few parents in the handle increases the probability
> + * that we'll find it in one of the MDS caches, but it is by no means
> + * a guarantee.
> + *
> + * Also, the FINDINODE request is currently directed at a single MDS.
> + * It should probably try all MDS's before giving up. For a single MDS
> + * system that isn't a problem.
> + *
> + * In the meantime, this works reasonably well for basic usage.
> + */
> +
> +
> +struct ceph_export_item {
> + struct ceph_vino ino;
> + struct ceph_vino parent_ino;
> + u32 parent_name_hash;
> +} __attribute__ ((packed));
> +
> +#define IPSZ ((sizeof(struct ceph_export_item) + sizeof(u32) + 1) / sizeof(u32))
> +
> +static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
> + int connectable)
> +{
> + int type = 1;
> + struct ceph_export_item *fh =
> + (struct ceph_export_item *)rawfh;
> + int max = *max_len / IPSZ;
> + int len;
> + struct dentry *d_parent;
> +
> + dout(10, "encode_fh %p max_len %d u32s (%d export items)%s\n", dentry,
> + *max_len, max, connectable ? " connectable" : "");
> +
> + if (max < 1 || (connectable && max < 2))
> + return -ENOSPC;
> +
> + for (len = 0; len < max; len++) {
> + d_parent = dentry->d_parent;
> + fh[len].ino = ceph_vino(dentry->d_inode);
> + fh[len].parent_ino = ceph_vino(d_parent->d_inode);
> + fh[len].parent_name_hash = dentry->d_parent->d_name.hash;
> +
> + if (IS_ROOT(dentry))
> + break;
> +
> + dentry = dentry->d_parent;
> +
> + if (!dentry)
> + break;
> + }
> +
> + if (len > 1)
> + type = 2;
> +
> + *max_len = len * IPSZ;
> + return type;
> +}
> +
> +static struct dentry *__fh_to_dentry(struct super_block *sb,
> + struct ceph_export_item *fh, int len)
> +{
> + struct ceph_mds_client *mdsc = &ceph_client(sb)->mdsc;
> + struct inode *inode;
> + struct dentry *dentry;
> + int err;
> +#define BUF_SIZE 16
> + char path2[BUF_SIZE];
> + u32 hash = fh->parent_name_hash;
> +
> + inode = ceph_find_inode(sb, fh->ino);
> + if (!inode) {
> + struct ceph_mds_request *req;
> + derr(10, "fh_to_dentry %llx.%x -- no inode\n", fh->ino.ino,
> + hash);
> + req = ceph_mdsc_create_request(mdsc, CEPH_MDS_OP_LOOKUPHASH,
> + USE_ANY_MDS);
> + if (IS_ERR(req))
> + return ERR_PTR(PTR_ERR(req));
> +
> + req->r_ino1 = fh->ino;
> + snprintf(path2, BUF_SIZE, "%d", hash);
> + req->r_ino2 = fh->parent_ino;
> + req->r_num_caps = 1;
> + err = ceph_mdsc_do_request(mdsc, NULL, req);
> + ceph_mdsc_put_request(req);
> + inode = ceph_find_inode(sb, fh->ino);
> + if (!inode)
> + return ERR_PTR(err ? err : -ESTALE);
> + }
> +
> + dentry = d_obtain_alias(inode);
> +
> + if (!dentry) {
> + derr(10, "fh_to_dentry %llx.%x -- inode %p but ENOMEM\n",
> + fh->ino.ino,
> + hash, inode);
> + iput(inode);
> + return ERR_PTR(-ENOMEM);
> + }
> + err = ceph_init_dentry(dentry);
> +
> + if (err < 0) {
> + iput(inode);
> + return ERR_PTR(err);
> + }
> + dout(10, "fh_to_dentry %llx.%x -- inode %p dentry %p\n", fh->ino.ino,
> + hash, inode, dentry);
> + return dentry;
> +
> +}
> +
> +static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
> + int fh_len, int fh_type)
> +{
> + u32 *fh = fid->raw;
> + return __fh_to_dentry(sb, (struct ceph_export_item *)fh, fh_len/IPSZ);
> +}
> +
> +static struct dentry *ceph_fh_to_parent(struct super_block *sb, struct fid *fid,
> + int fh_len, int fh_type)
> +{
> + u32 *fh = fid->raw;
> + u64 ino = get_unaligned((u64 *)fh);
> + u32 hash = fh[2];
> +
> + derr(10, "fh_to_parent %llx.%x\n", (unsigned long long)ino, hash);
> +
> + if (fh_len < 6)
> + return ERR_PTR(-ESTALE);
> +
> + return __fh_to_dentry(sb, (struct ceph_export_item *)fh + 1,
> + fh_len/IPSZ - 1);
> +}
> +
> +const struct export_operations ceph_export_ops = {
> + .encode_fh = ceph_encode_fh,
> + .fh_to_dentry = ceph_fh_to_dentry,
> + .fh_to_parent = ceph_fh_to_parent,
> +};
> --
> 1.5.6.5
>
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