From: Darrick J. Wong <djwong@xxxxxxxxxx>
The current definition of the GETPARENTS ioctl doesn't use the buffer
space terribly efficiently because each parent pointer record struct
incorporates enough space to hold the maximally sized dirent name. Most
dirent names are much less than 255 bytes long, which means we're
wasting a lot of space.
Convert the xfs_getparents_rec structure to use a flex array to store
the dirent name as a null terminated string, which allows us to pack the
information much more densely. For this to work, augment the
xfs_getparents struct to end with a flex array of buffer offsets to each
xfs_getparents_rec object, much as we do for the attrlist multi ioctl.
Record objects are allocated from the end of the buffer towards the
head.
Reduce the amount of data that we copy to userspace to the head array
containg the offsets, and however much of the buffer's end is used for
the parent records.
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
libfrog/pptrs.c | 12 ++++++------
libxfs/xfs_fs.h | 38 ++++++++++++++------------------------
2 files changed, 20 insertions(+), 30 deletions(-)
diff --git a/libfrog/pptrs.c b/libfrog/pptrs.c
index 48a09f69..67fd40c3 100644
--- a/libfrog/pptrs.c
+++ b/libfrog/pptrs.c
@@ -14,15 +14,15 @@
/* Allocate a buffer large enough for some parent pointer records. */
static inline struct xfs_getparents *
alloc_pptr_buf(
- size_t nr_ptrs)
+ size_t bufsize)
{
struct xfs_getparents *pi;
- pi = malloc(xfs_getparents_sizeof(nr_ptrs));
+ pi = calloc(bufsize, 1);
if (!pi)
return NULL;
- memset(pi, 0, sizeof(struct xfs_getparents));
- pi->gp_ptrs_size = nr_ptrs;
+
+ pi->gp_bufsize = bufsize;
return pi;
}
@@ -42,7 +42,7 @@ handle_walk_parents(
unsigned int i;
ssize_t ret = -1;
- pi = alloc_pptr_buf(4);
+ pi = alloc_pptr_buf(XFS_XATTR_LIST_MAX);
if (!pi)
return errno;
@@ -58,7 +58,7 @@ handle_walk_parents(
goto out_pi;
}
- for (i = 0; i < pi->gp_ptrs_used; i++) {
+ for (i = 0; i < pi->gp_count; i++) {
p = xfs_getparents_rec(pi, i);
ret = fn(pi, p, arg);
if (ret)
diff --git a/libxfs/xfs_fs.h b/libxfs/xfs_fs.h
index ec6fdf78..c8be1493 100644
--- a/libxfs/xfs_fs.h
+++ b/libxfs/xfs_fs.h
@@ -769,11 +769,11 @@ struct xfs_scrub_metadata {
/* Get an inode parent pointer through ioctl */
struct xfs_getparents_rec {
- __u64 gpr_ino; /* Inode */
- __u32 gpr_gen; /* Inode generation */
- __u32 gpr_rsvd; /* Reserved */
- __u64 gpr_rsvd2; /* Reserved */
- __u8 gpr_name[XFS_GETPARENTS_MAXNAMELEN]; /* File name */
+ __u64 gpr_ino; /* Inode */
+ __u32 gpr_gen; /* Inode generation */
+ __u32 gpr_rsvd; /* Reserved */
+ __u64 gpr_rsvd2; /* Reserved */
+ __u8 gpr_name[]; /* File name and null terminator */
};
/* Iterate through an inodes parent pointers */
@@ -794,36 +794,26 @@ struct xfs_getparents {
/* Must be set to zero */
__u32 gp_reserved;
- /* # of entries in array */
- __u32 gp_ptrs_size;
+ /* size of the memory buffer in bytes, including this header */
+ __u32 gp_bufsize;
/* # of entries filled in (output) */
- __u32 gp_ptrs_used;
+ __u32 gp_count;
/* Must be set to zero */
- __u64 gp_reserved2[6];
+ __u64 gp_reserved2[5];
- /*
- * An array of struct xfs_getparents_rec follows the header
- * information. Use xfs_getparents_rec() to access the
- * parent pointer array entries.
- */
- struct xfs_getparents_rec gp_parents[];
+ /* Byte offset of each xfs_getparents_rec object within the buffer. */
+ __u32 gp_offsets[];
};
-static inline size_t
-xfs_getparents_sizeof(int nr_ptrs)
-{
- return sizeof(struct xfs_getparents) +
- (nr_ptrs * sizeof(struct xfs_getparents_rec));
-}
-
static inline struct xfs_getparents_rec*
xfs_getparents_rec(
struct xfs_getparents *info,
unsigned int idx)
{
- return &info->gp_parents[idx];
+ return (struct xfs_getparents_rec *)((char *)info +
+ info->gp_offsets[idx]);
}
/*
@@ -871,7 +861,7 @@ xfs_getparents_rec(
/* XFS_IOC_GETFSMAP ------ hoisted 59 */
#define XFS_IOC_SCRUB_METADATA _IOWR('X', 60, struct xfs_scrub_metadata)
#define XFS_IOC_AG_GEOMETRY _IOWR('X', 61, struct xfs_ag_geometry)
-#define XFS_IOC_GETPARENTS _IOWR('X', 62, struct xfs_getparents_rec)
+#define XFS_IOC_GETPARENTS _IOWR('X', 62, struct xfs_getparents)
/*
* ioctl commands that replace IRIX syssgi()'s
