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    SubjectRe: [PATCH 16/20] ceph: nfs re-export support
    From
    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@newdream.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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