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    Subject[PATCH 18/21] ceph: nfs re-export support
    Date
    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.

    Signed-off-by: Sage Weil <sage@newdream.net>
    ---
    fs/ceph/export.c | 222 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
    1 files changed, 222 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..f768810
    --- /dev/null
    +++ b/fs/ceph/export.c
    @@ -0,0 +1,222 @@
    +#include <linux/exportfs.h>
    +#include <asm/unaligned.h>
    +
    +#include "super.h"
    +#include "ceph_debug.h"
    +
    +/*
    + * NFS export support
    + *
    + * NFS re-export of a ceph mount is, at present, only semireliable.
    + * The basic issue is that the Ceph architectures doesn't lend itself
    + * well to generating filehandles that will remain valid forever.
    + *
    + * So, we do our best. If you're lucky, your inode will be in the
    + * client's cache. If it's not, and you have a connectable fh, then
    + * the MDS server may be able to find it for you. Otherwise, you get
    + * ESTALE.
    + *
    + * There are ways to this more reliable, but in the non-connectable fh
    + * case, we won't every work perfectly, and in the connectable case,
    + * some changes are needed on the MDS side to work better.
    + */
    +
    +/*
    + * Basic fh
    + */
    +struct ceph_nfs_fh {
    + u64 ino;
    +} __attribute__ ((packed));
    +
    +/*
    + * Larger 'connectable' fh that includes parent ino and name hash.
    + * Use this whenever possible, as it works more reliably.
    + */
    +struct ceph_nfs_confh {
    + u64 ino, parent_ino;
    + u32 parent_name_hash;
    +} __attribute__ ((packed));
    +
    +static int ceph_encode_fh(struct dentry *dentry, u32 *rawfh, int *max_len,
    + int connectable)
    +{
    + struct ceph_nfs_fh *fh = (void *)rawfh;
    + struct ceph_nfs_confh *cfh = (void *)rawfh;
    + struct dentry *parent = dentry->d_parent;
    + struct inode *inode = dentry->d_inode;
    + int type;
    +
    + /* don't re-export snaps */
    + if (ceph_snap(inode) != CEPH_NOSNAP)
    + return -EINVAL;
    +
    + if (*max_len >= sizeof(*cfh)) {
    + dout("encode_fh %p connectable\n", dentry);
    + cfh->ino = ceph_ino(dentry->d_inode);
    + cfh->parent_ino = ceph_ino(parent->d_inode);
    + cfh->parent_name_hash = parent->d_name.hash;
    + *max_len = sizeof(*cfh);
    + type = 2;
    + } else if (*max_len > sizeof(*fh)) {
    + if (connectable)
    + return -ENOSPC;
    + dout("encode_fh %p\n", dentry);
    + fh->ino = ceph_ino(dentry->d_inode);
    + *max_len = sizeof(*fh);
    + type = 1;
    + } else {
    + return -ENOSPC;
    + }
    + return type;
    +}
    +
    +/*
    + * convert regular fh to dentry
    + *
    + * FIXME: we should try harder by querying the mds for the ino.
    + */
    +static struct dentry *__fh_to_dentry(struct super_block *sb,
    + struct ceph_nfs_fh *fh)
    +{
    + struct inode *inode;
    + struct dentry *dentry;
    + struct ceph_vino vino;
    + int err;
    +
    + dout("__fh_to_dentry %llx\n", fh->ino);
    + vino.ino = fh->ino;
    + vino.snap = CEPH_NOSNAP;
    + inode = ceph_find_inode(sb, vino);
    + if (!inode)
    + return ERR_PTR(-ESTALE);
    +
    + dentry = d_obtain_alias(inode);
    + if (!dentry) {
    + pr_err("ceph fh_to_dentry %llx -- inode %p but ENOMEM\n",
    + fh->ino, inode);
    + iput(inode);
    + return ERR_PTR(-ENOMEM);
    + }
    + err = ceph_init_dentry(dentry);
    +
    + if (err < 0) {
    + iput(inode);
    + return ERR_PTR(err);
    + }
    + dout("__fh_to_dentry %llx %p dentry %p\n", fh->ino, inode, dentry);
    + return dentry;
    +}
    +
    +/*
    + * convert connectable fh to dentry
    + */
    +static struct dentry *__cfh_to_dentry(struct super_block *sb,
    + struct ceph_nfs_confh *cfh)
    +{
    + struct ceph_mds_client *mdsc = &ceph_client(sb)->mdsc;
    + struct inode *inode;
    + struct dentry *dentry;
    + struct ceph_vino vino;
    + int err;
    +
    + dout("__cfh_to_dentry %llx (%llx/%x)\n",
    + cfh->ino, cfh->parent_ino, cfh->parent_name_hash);
    +
    + vino.ino = cfh->ino;
    + vino.snap = CEPH_NOSNAP;
    + inode = ceph_find_inode(sb, vino);
    + if (!inode) {
    + struct ceph_mds_request *req;
    +
    + 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 = vino;
    + req->r_ino2.ino = cfh->parent_ino;
    + req->r_ino2.snap = CEPH_NOSNAP;
    + req->r_path2 = kmalloc(16, GFP_NOFS);
    + snprintf(req->r_path2, 16, "%d", cfh->parent_name_hash);
    + req->r_num_caps = 1;
    + err = ceph_mdsc_do_request(mdsc, NULL, req);
    + ceph_mdsc_put_request(req);
    + inode = ceph_find_inode(sb, vino);
    + if (!inode)
    + return ERR_PTR(err ? err : -ESTALE);
    + }
    +
    + dentry = d_obtain_alias(inode);
    + if (!dentry) {
    + pr_err("ceph cfh_to_dentry %llx -- inode %p but ENOMEM\n",
    + cfh->ino, inode);
    + iput(inode);
    + return ERR_PTR(-ENOMEM);
    + }
    + err = ceph_init_dentry(dentry);
    + if (err < 0) {
    + iput(inode);
    + return ERR_PTR(err);
    + }
    + dout("__cfh_to_dentry %llx %p dentry %p\n", cfh->ino, inode, dentry);
    + return dentry;
    +}
    +
    +static struct dentry *ceph_fh_to_dentry(struct super_block *sb, struct fid *fid,
    + int fh_len, int fh_type)
    +{
    + if (fh_type == 1)
    + return __fh_to_dentry(sb, (struct ceph_nfs_fh *)fid->raw);
    + else
    + return __cfh_to_dentry(sb, (struct ceph_nfs_confh *)fid->raw);
    +}
    +
    +/*
    + * get parent, if possible.
    + *
    + * FIXME: we could do better by querying the mds to discover the
    + * parent.
    + */
    +static struct dentry *ceph_fh_to_parent(struct super_block *sb,
    + struct fid *fid,
    + int fh_len, int fh_type)
    +{
    + struct ceph_nfs_confh *cfh = (void *)fid->raw;
    + struct ceph_vino vino;
    + struct inode *inode;
    + struct dentry *dentry;
    + int err;
    +
    + if (fh_type == 1)
    + return ERR_PTR(-ESTALE);
    +
    + pr_debug("ceph_fh_to_parent %llx/%d\n", cfh->parent_ino,
    + cfh->parent_name_hash);
    +
    + vino.ino = cfh->ino;
    + vino.snap = CEPH_NOSNAP;
    + inode = ceph_find_inode(sb, vino);
    + if (!inode)
    + return ERR_PTR(-ESTALE);
    +
    + dentry = d_obtain_alias(inode);
    + if (!dentry) {
    + pr_err("ceph fh_to_parent %llx -- inode %p but ENOMEM\n",
    + cfh->ino, inode);
    + iput(inode);
    + return ERR_PTR(-ENOMEM);
    + }
    + err = ceph_init_dentry(dentry);
    + if (err < 0) {
    + iput(inode);
    + return ERR_PTR(err);
    + }
    + dout("fh_to_parent %llx %p dentry %p\n", cfh->ino, inode, dentry);
    + return dentry;
    +}
    +
    +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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