On 11/22/2017 02:07 PM, Dave Chinner wrote:
On Wed, Nov 22, 2017 at 12:54:45PM -0700, Allison Henderson wrote:
On 11/17/2017 11:21 AM, Allison Henderson wrote:
This patch adds a new file ioctl to retrieve the parent
pointer of a given inode
Signed-off-by: Allison Henderson <allison.henderson@xxxxxxxxxx>
---
fs/xfs/libxfs/xfs_attr.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/xfs/libxfs/xfs_fs.h | 1 +
fs/xfs/xfs_attr.h | 2 ++
fs/xfs/xfs_attr_list.c | 3 +++
fs/xfs/xfs_ioctl.c | 48 +++++++++++++++++++++++++++++++++-
5 files changed, 120 insertions(+), 1 deletion(-)
diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
index 9d4d883..d2be842 100644
--- a/fs/xfs/libxfs/xfs_attr.c
+++ b/fs/xfs/libxfs/xfs_attr.c
@@ -134,6 +134,73 @@ xfs_attr_get_ilocked(
return xfs_attr_node_get(args);
}
+/*
+ * Get the parent pointer for a given inode
+ * Caller will need to allocate a buffer pointed to by xpnir->p_name
+ * and store the buffer size in xpnir->p_namelen. The parent
+ * pointer will be stored in the given xfs_parent_name_irec
+ *
+ * Returns 0 on success and non zero on error
+ */
+int
+xfs_attr_get_parent_pointer(struct xfs_inode *ip,
+ struct xfs_parent_name_irec *xpnir)
+{
+ struct attrlist *alist;
+ struct attrlist_ent *aent;
+ struct attrlist_cursor_kern cursor;
+ struct xfs_parent_name_rec *xpnr;
+ char *namebuf;
+ int error = 0;
+ unsigned int flags = ATTR_PARENT;
+
+ /* Allocate a buffer to store the attribute names */
+ namebuf = kmem_zalloc_large(XFS_XATTR_LIST_MAX, KM_SLEEP);
+ if (!namebuf)
+ return -ENOMEM;
+
+ /* Get all attribute names that have the ATTR_PARENT flag */
+ memset(&cursor, 0, sizeof(struct attrlist_cursor_kern));
+ error = xfs_attr_list(ip, namebuf, XFS_XATTR_LIST_MAX, flags, &cursor);
+ if (error)
+ goto out_kfree;
+
+ alist = (struct attrlist *)namebuf;
+
+ /* There should never be more than one parent pointer */
+ ASSERT(alist->al_count == 1);
+
+ aent = (struct attrlist_ent *) &namebuf[alist->al_offset[0]];
+ xpnr = (struct xfs_parent_name_rec *)(aent->a_name);
+
+ /*
+ * The value of the parent pointer attribute should be the file name
+ * So we check the value length of the attribute entry against the name
+ * length of the parent name record to make sure the caller gave enough
+ * buffer space to store the file name (plus a null terminator)
+ */
+ if (aent->a_valuelen >= xpnir->p_namelen) {
+ error = -ERANGE;
+ goto out_kfree;
+ }
+
+ xpnir->p_namelen = aent->a_valuelen + 1;
+ memset((void *)(xpnir->p_name), 0, xpnir->p_namelen);
+ error = xfs_attr_get(ip, (char *)xpnr,
+ sizeof(struct xfs_parent_name_rec),
+ (unsigned char *)(xpnir->p_name),
+ (int *)&(xpnir->p_namelen), flags);
+ if (error)
+ goto out_kfree;
+
+ xfs_init_parent_name_irec(xpnir, xpnr);
+
+out_kfree:
+ kmem_free(namebuf);
+
+ return error;
+}
I was thinking of moving this function else where. It seems to
generate a lot of compile issues when I apply it to xfsprogs because
of the things it needs from xfs_attr.h. Generally are patches to
code in fs/xfs/libxfs not supposed to be including things outside
libxfs? Do I need to revise the series to avoid doing that? Thanks!
In general, yes. More complex than that (e.g. userspace and kernel
have separate definitions of some structures like xfs_mount,
xfs_buf, etc), but we try to keep the libxfs code as encapsulated as
possible.
In terms of getting attrs to userspace, the equivalent attribute
listing code is in fs/xfs/xfs_attr_list.c, and that avoids all these
problems. I'd just move the xfs_attr_get_parent_pointer() function
there as ithis code should not be needed in userspace and it would
avoid all the userspace libxfs compile issues...
Cheers,
Dave.
Alrighty, that seems like a good place for it then. Thank you!
Allison
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