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[PATCH 1/2] repair: fix the variable-width nlink array

To: xfs@xxxxxxxxxxx
Subject: [PATCH 1/2] repair: fix the variable-width nlink array
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Tue, 28 Feb 2012 12:42:24 -0500
User-agent: Mutt/1.5.21 (2010-09-15)
It looks like we currently never grow the variable-width nlink array
if only the on-disk nlink size overflows 8 bits.  This leads to a major
mess in nlink counting, and eventually an assert in phase7.

Replace the indirect all mess with a union that allows doing proper
array arithmetics while we're at it.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>

diff --git a/repair/incore.h b/repair/incore.h
index fdb7742..8a578b5 100644
--- a/repair/incore.h
+++ b/repair/incore.h
@@ -268,11 +268,17 @@ typedef struct parent_list  {
 #endif
 } parent_list_t;
 
+union ino_nlink {
+       __uint8_t       *un8;
+       __uint16_t      *un16;
+       __uint32_t      *un32;
+};
+
 typedef struct ino_ex_data  {
        __uint64_t              ino_reached;    /* bit == 1 if reached */
        __uint64_t              ino_processed;  /* reference checked bit mask */
        parent_list_t           *parents;
-       __uint8_t               *counted_nlinks;/* counted nlinks in P6 */
+       union ino_nlink         counted_nlinks;/* counted nlinks in P6 */
 } ino_ex_data_t;
 
 typedef struct ino_tree_node  {
@@ -281,8 +287,8 @@ typedef struct ino_tree_node  {
        xfs_inofree_t           ir_free;        /* inode free bit mask */
        __uint64_t              ino_confirmed;  /* confirmed bitmask */
        __uint64_t              ino_isa_dir;    /* bit == 1 if a directory */
-       struct nlink_ops        *nlinkops;      /* pointer to current nlink ops 
*/
-       __uint8_t               *disk_nlinks;   /* on-disk nlinks, set in P3 */
+       __uint8_t               nlink_size;
+       union ino_nlink         disk_nlinks;    /* on-disk nlinks, set in P3 */
        union  {
                ino_ex_data_t   *ex_data;       /* phases 6,7 */
                parent_list_t   *plist;         /* phases 2-5 */
@@ -292,16 +298,6 @@ typedef struct ino_tree_node  {
 #define INOS_PER_IREC  (sizeof(__uint64_t) * NBBY)
 #define        IREC_MASK(i)    ((__uint64_t)1 << (i))
 
-typedef struct nlink_ops {
-       const int       nlink_size;
-       void            (*disk_nlink_set)(ino_tree_node_t *, int, __uint32_t);
-       __uint32_t      (*disk_nlink_get)(ino_tree_node_t *, int);
-       __uint32_t      (*counted_nlink_get)(ino_tree_node_t *, int);
-       __uint32_t      (*counted_nlink_inc)(ino_tree_node_t *, int);
-       __uint32_t      (*counted_nlink_dec)(ino_tree_node_t *, int);
-} nlink_ops_t;
-
-
 void           add_ino_ex_data(xfs_mount_t *mp);
 
 /*
@@ -460,29 +456,12 @@ static inline int is_inode_free(struct ino_tree_node 
*irec, int offset)
  * detected and drop_inode_ref() is called every time a link to
  * an inode that we've counted is removed.
  */
+void add_inode_ref(struct ino_tree_node *irec, int offset);
+void drop_inode_ref(struct ino_tree_node *irec, int offset);
+__uint32_t num_inode_references(struct ino_tree_node *irec, int offset);
 
-static inline void add_inode_ref(struct ino_tree_node *irec, int offset)
-{
-       ASSERT(irec->ino_un.ex_data != NULL);
-
-       irec->nlinkops->counted_nlink_inc(irec, offset);
-}
-
-static inline void drop_inode_ref(struct ino_tree_node *irec, int offset)
-{
-       ASSERT(irec->ino_un.ex_data != NULL);
-
-       if (irec->nlinkops->counted_nlink_dec(irec, offset) == 0)
-               irec->ino_un.ex_data->ino_reached &= ~IREC_MASK(offset);
-}
-
-static inline __uint32_t num_inode_references(struct ino_tree_node *irec,
-               int offset)
-{
-       ASSERT(irec->ino_un.ex_data != NULL);
-
-       return irec->nlinkops->counted_nlink_get(irec, offset);
-}
+void set_inode_disk_nlinks(struct ino_tree_node *irec, int offset, __uint32_t 
nlinks);
+__uint32_t get_inode_disk_nlinks(struct ino_tree_node *irec, int offset);
 
 static inline int is_inode_reached(struct ino_tree_node *irec, int offset)
 {
@@ -496,18 +475,6 @@ static inline void add_inode_reached(struct ino_tree_node 
*irec, int offset)
        irec->ino_un.ex_data->ino_reached |= IREC_MASK(offset);
 }
 
-static inline void set_inode_disk_nlinks(struct ino_tree_node *irec, int 
offset,
-               __uint32_t nlinks)
-{
-       irec->nlinkops->disk_nlink_set(irec, offset, nlinks);
-}
-
-static inline __uint32_t get_inode_disk_nlinks(struct ino_tree_node *irec,
-               int offset)
-{
-       return irec->nlinkops->disk_nlink_get(irec, offset);
-}
-
 /*
  * set/get inode number of parent -- works for directory inodes only
  */
diff --git a/repair/incore_ino.c b/repair/incore_ino.c
index b933765..2a40727 100644
--- a/repair/incore_ino.c
+++ b/repair/incore_ino.c
@@ -37,189 +37,176 @@ static avltree_desc_t     **inode_uncertain_tree_ptrs;
 
 /* memory optimised nlink counting for all inodes */
 
-static void nlink_grow_8_to_16(ino_tree_node_t *irec);
-static void nlink_grow_16_to_32(ino_tree_node_t *irec);
-
-static void
-disk_nlink_32_set(ino_tree_node_t *irec, int ino_offset, __uint32_t nlinks)
+static void *
+alloc_nlink_array(__uint8_t nlink_size)
 {
-       ((__uint32_t*)irec->disk_nlinks)[ino_offset] = nlinks;
-}
+       void *ptr;
 
-static __uint32_t
-disk_nlink_32_get(ino_tree_node_t *irec, int ino_offset)
-{
-       return ((__uint32_t*)irec->disk_nlinks)[ino_offset];
+       ptr = calloc(XFS_INODES_PER_CHUNK, nlink_size);
+       if (!ptr)
+               do_error(_("could not allocate nlink array\n"));
+       return ptr;
 }
 
-static __uint32_t
-counted_nlink_32_get(ino_tree_node_t *irec, int ino_offset)
+static void
+nlink_grow_8_to_16(ino_tree_node_t *irec)
 {
-       return ((__uint32_t*)irec->ino_un.ex_data->counted_nlinks)[ino_offset];
-}
+       __uint16_t      *new_nlinks;
+       int             i;
 
-static __uint32_t
-counted_nlink_32_inc(ino_tree_node_t *irec, int ino_offset)
-{
-       return 
++(((__uint32_t*)irec->ino_un.ex_data->counted_nlinks)[ino_offset]);
-}
+       irec->nlink_size = sizeof(__uint16_t);
 
-static __uint32_t
-counted_nlink_32_dec(ino_tree_node_t *irec, int ino_offset)
-{
-       __uint32_t *nlinks = (__uint32_t*)irec->ino_un.ex_data->counted_nlinks;
+       new_nlinks = alloc_nlink_array(irec->nlink_size);
+       for (i = 0; i < XFS_INODES_PER_CHUNK; i++)
+               new_nlinks[i] = irec->disk_nlinks.un8[i];
+       free(irec->disk_nlinks.un8);
+       irec->disk_nlinks.un16 = new_nlinks;
 
-       ASSERT(nlinks[ino_offset] > 0);
-       return --(nlinks[ino_offset]);
+       if (full_ino_ex_data) {
+               new_nlinks = alloc_nlink_array(irec->nlink_size);
+               for (i = 0; i < XFS_INODES_PER_CHUNK; i++) {
+                       new_nlinks[i] =
+                               irec->ino_un.ex_data->counted_nlinks.un8[i];
+               }
+               free(irec->ino_un.ex_data->counted_nlinks.un8);
+               irec->ino_un.ex_data->counted_nlinks.un16 = new_nlinks;
+       }
 }
 
-
 static void
-disk_nlink_16_set(ino_tree_node_t *irec, int ino_offset, __uint32_t nlinks)
+nlink_grow_16_to_32(ino_tree_node_t *irec)
 {
-       if (nlinks >= 0x10000) {
-               nlink_grow_16_to_32(irec);
-               disk_nlink_32_set(irec, ino_offset, nlinks);
-       } else
-               ((__uint16_t*)irec->disk_nlinks)[ino_offset] = nlinks;
-}
+       __uint32_t      *new_nlinks;
+       int             i;
 
-static __uint32_t
-disk_nlink_16_get(ino_tree_node_t *irec, int ino_offset)
-{
-       return ((__uint16_t*)irec->disk_nlinks)[ino_offset];
-}
+       irec->nlink_size = sizeof(__uint32_t);
 
-static __uint32_t
-counted_nlink_16_get(ino_tree_node_t *irec, int ino_offset)
-{
-       return ((__uint16_t*)irec->ino_un.ex_data->counted_nlinks)[ino_offset];
-}
+       new_nlinks = alloc_nlink_array(irec->nlink_size);
+       for (i = 0; i < XFS_INODES_PER_CHUNK; i++)
+               new_nlinks[i] = irec->disk_nlinks.un16[i];
+       free(irec->disk_nlinks.un16);
+       irec->disk_nlinks.un32 = new_nlinks;
 
-static __uint32_t
-counted_nlink_16_inc(ino_tree_node_t *irec, int ino_offset)
-{
-       __uint16_t *nlinks = (__uint16_t*)irec->ino_un.ex_data->counted_nlinks;
+       if (full_ino_ex_data) {
+               new_nlinks = alloc_nlink_array(irec->nlink_size);
 
-       if (nlinks[ino_offset] == 0xffff) {
-               nlink_grow_16_to_32(irec);
-               return counted_nlink_32_inc(irec, ino_offset);
+               for (i = 0; i < XFS_INODES_PER_CHUNK; i++) {
+                       new_nlinks[i] =
+                               irec->ino_un.ex_data->counted_nlinks.un16[i];
+               }
+               free(irec->ino_un.ex_data->counted_nlinks.un16);
+               irec->ino_un.ex_data->counted_nlinks.un32 = new_nlinks;
        }
-       return ++(nlinks[ino_offset]);
 }
 
-static __uint32_t
-counted_nlink_16_dec(ino_tree_node_t *irec, int ino_offset)
+void add_inode_ref(struct ino_tree_node *irec, int ino_offset)
 {
-       __uint16_t *nlinks = (__uint16_t*)irec->ino_un.ex_data->counted_nlinks;
-
-       ASSERT(nlinks[ino_offset] > 0);
-       return --(nlinks[ino_offset]);
-}
-
+       ASSERT(irec->ino_un.ex_data != NULL);
 
-static void
-disk_nlink_8_set(ino_tree_node_t *irec, int ino_offset, __uint32_t nlinks)
-{
-       if (nlinks >= 0x100) {
+       switch (irec->nlink_size) {
+       case sizeof(__uint8_t):
+               if (irec->ino_un.ex_data->counted_nlinks.un8[ino_offset] < 
0xff) {
+                       irec->ino_un.ex_data->counted_nlinks.un8[ino_offset]++;
+                       break;
+               }
                nlink_grow_8_to_16(irec);
-               disk_nlink_16_set(irec, ino_offset, nlinks);
-       } else
-               irec->disk_nlinks[ino_offset] = nlinks;
+               /*FALLTHRU*/
+       case sizeof(__uint16_t):
+               if (irec->ino_un.ex_data->counted_nlinks.un16[ino_offset] < 
0xffff) {
+                       irec->ino_un.ex_data->counted_nlinks.un16[ino_offset]++;
+                       break;
+               }
+               nlink_grow_16_to_32(irec);
+               /*FALLTHRU*/
+       case sizeof(__uint32_t):
+               irec->ino_un.ex_data->counted_nlinks.un32[ino_offset]++;
+               break;
+       default:
+               ASSERT(0);
+       }
 }
 
-static __uint32_t
-disk_nlink_8_get(ino_tree_node_t *irec, int ino_offset)
+void drop_inode_ref(struct ino_tree_node *irec, int ino_offset)
 {
-       return irec->disk_nlinks[ino_offset];
-}
+       __uint32_t      refs = 0;
 
-static __uint32_t
-counted_nlink_8_get(ino_tree_node_t *irec, int ino_offset)
-{
-       return irec->ino_un.ex_data->counted_nlinks[ino_offset];
-}
+       ASSERT(irec->ino_un.ex_data != NULL);
 
-static __uint32_t
-counted_nlink_8_inc(ino_tree_node_t *irec, int ino_offset)
-{
-       if (irec->ino_un.ex_data->counted_nlinks[ino_offset] == 0xff) {
-               nlink_grow_8_to_16(irec);
-               return counted_nlink_16_inc(irec, ino_offset);
+       switch (irec->nlink_size) {
+       case sizeof(__uint8_t):
+               ASSERT(irec->ino_un.ex_data->counted_nlinks.un8[ino_offset] > 
0);
+               refs = --irec->ino_un.ex_data->counted_nlinks.un8[ino_offset];
+               break;
+       case sizeof(__uint16_t):
+               ASSERT(irec->ino_un.ex_data->counted_nlinks.un16[ino_offset] > 
0);
+               refs = --irec->ino_un.ex_data->counted_nlinks.un16[ino_offset];
+               break;
+       case sizeof(__uint32_t):
+               ASSERT(irec->ino_un.ex_data->counted_nlinks.un32[ino_offset] > 
0);
+               refs = --irec->ino_un.ex_data->counted_nlinks.un32[ino_offset];
+               break;
+       default:
+               ASSERT(0);
        }
-       return ++(irec->ino_un.ex_data->counted_nlinks[ino_offset]);
-}
 
-static __uint32_t
-counted_nlink_8_dec(ino_tree_node_t *irec, int ino_offset)
-{
-       ASSERT(irec->ino_un.ex_data->counted_nlinks[ino_offset] > 0);
-       return --(irec->ino_un.ex_data->counted_nlinks[ino_offset]);
+       if (refs == 0)
+               irec->ino_un.ex_data->ino_reached &= ~IREC_MASK(ino_offset);
 }
 
-
-static nlink_ops_t nlinkops[] = {
-       {sizeof(__uint8_t) * XFS_INODES_PER_CHUNK,
-               disk_nlink_8_set, disk_nlink_8_get,
-               counted_nlink_8_get, counted_nlink_8_inc, counted_nlink_8_dec},
-       {sizeof(__uint16_t) * XFS_INODES_PER_CHUNK,
-               disk_nlink_16_set, disk_nlink_16_get,
-               counted_nlink_16_get, counted_nlink_16_inc, 
counted_nlink_16_dec},
-       {sizeof(__uint32_t) * XFS_INODES_PER_CHUNK,
-               disk_nlink_32_set, disk_nlink_32_get,
-               counted_nlink_32_get, counted_nlink_32_inc, 
counted_nlink_32_dec},
-};
-
-static void
-nlink_grow_8_to_16(ino_tree_node_t *irec)
+__uint32_t num_inode_references(struct ino_tree_node *irec, int ino_offset)
 {
-       __uint16_t      *new_nlinks;
-       int             i;
+       ASSERT(irec->ino_un.ex_data != NULL);
 
-       new_nlinks = malloc(sizeof(__uint16_t) * XFS_INODES_PER_CHUNK);
-       if (new_nlinks == NULL)
-               do_error(_("could not allocate expanded nlink array\n"));
-       for (i = 0; i < XFS_INODES_PER_CHUNK; i++)
-               new_nlinks[i] = irec->disk_nlinks[i];
-       free(irec->disk_nlinks);
-       irec->disk_nlinks = (__uint8_t*)new_nlinks;
-
-       if (full_ino_ex_data) {
-               new_nlinks = malloc(sizeof(__uint16_t) * XFS_INODES_PER_CHUNK);
-               if (new_nlinks == NULL)
-                       do_error(_("could not allocate expanded nlink 
array\n"));
-               for (i = 0; i < XFS_INODES_PER_CHUNK; i++)
-                       new_nlinks[i] = irec->ino_un.ex_data->counted_nlinks[i];
-               free(irec->ino_un.ex_data->counted_nlinks);
-               irec->ino_un.ex_data->counted_nlinks = (__uint8_t*)new_nlinks;
+       switch (irec->nlink_size) {
+       case sizeof(__uint8_t):
+               return irec->ino_un.ex_data->counted_nlinks.un8[ino_offset];
+       case sizeof(__uint16_t):
+               return irec->ino_un.ex_data->counted_nlinks.un16[ino_offset];
+       case sizeof(__uint32_t):
+               return irec->ino_un.ex_data->counted_nlinks.un32[ino_offset];
+       default:
+               ASSERT(0);
        }
-       irec->nlinkops = &nlinkops[1];
 }
 
-static void
-nlink_grow_16_to_32(ino_tree_node_t *irec)
+void set_inode_disk_nlinks(struct ino_tree_node *irec, int ino_offset,
+               __uint32_t nlinks)
 {
-       __uint32_t      *new_nlinks;
-       int             i;
-
-       new_nlinks = malloc(sizeof(__uint32_t) * XFS_INODES_PER_CHUNK);
-       if (new_nlinks == NULL)
-               do_error(_("could not allocate expanded nlink array\n"));
-       for (i = 0; i < XFS_INODES_PER_CHUNK; i++)
-               new_nlinks[i] = ((__int16_t*)&irec->disk_nlinks)[i];
-       free(irec->disk_nlinks);
-       irec->disk_nlinks = (__uint8_t*)new_nlinks;
+       switch (irec->nlink_size) {
+       case sizeof(__uint8_t):
+               if (nlinks < 0xff) {
+                       irec->disk_nlinks.un8[ino_offset] = nlinks;
+                       break;
+               }
+               nlink_grow_8_to_16(irec);
+               /*FALLTHRU*/
+       case sizeof(__uint16_t):
+               if (nlinks < 0xffff) {
+                       irec->disk_nlinks.un16[ino_offset] = nlinks;
+                       break;
+               }
+               nlink_grow_16_to_32(irec);
+               /*FALLTHRU*/
+       case sizeof(__uint32_t):
+               irec->disk_nlinks.un32[ino_offset] = nlinks;
+               break;
+       default:
+               ASSERT(0);
+       }
+}
 
-       if (full_ino_ex_data) {
-               new_nlinks = malloc(sizeof(__uint32_t) * XFS_INODES_PER_CHUNK);
-               if (new_nlinks == NULL)
-                       do_error(_("could not allocate expanded nlink 
array\n"));
-               for (i = 0; i < XFS_INODES_PER_CHUNK; i++)
-                       new_nlinks[i] = 
((__int16_t*)&irec->ino_un.ex_data->counted_nlinks)[i];
-               free(irec->ino_un.ex_data->counted_nlinks);
-               irec->ino_un.ex_data->counted_nlinks = (__uint8_t*)new_nlinks;
+__uint32_t get_inode_disk_nlinks(struct ino_tree_node *irec, int ino_offset)
+{
+       switch (irec->nlink_size) {
+       case sizeof(__uint8_t):
+               return irec->disk_nlinks.un8[ino_offset];
+       case sizeof(__uint16_t):
+               return irec->disk_nlinks.un16[ino_offset];
+       case sizeof(__uint32_t):
+               return irec->disk_nlinks.un32[ino_offset];
+       default:
+               ASSERT(0);
        }
-       irec->nlinkops = &nlinkops[2];
 }
 
 /*
@@ -254,14 +241,30 @@ alloc_ino_node(
        irec->ino_isa_dir = 0;
        irec->ir_free = (xfs_inofree_t) - 1;
        irec->ino_un.ex_data = NULL;
-       irec->nlinkops = &nlinkops[0];
-       irec->disk_nlinks = calloc(1, nlinkops[0].nlink_size);
-       if (!irec->disk_nlinks)
-               do_error(_("could not allocate nlink array\n"));
+       irec->nlink_size = sizeof(__uint8_t);
+       irec->disk_nlinks.un8 = alloc_nlink_array(irec->nlink_size);
        return irec;
 }
 
 static void
+free_nlink_array(union ino_nlink nlinks, __uint8_t nlink_size)
+{
+       switch (nlink_size) {
+       case sizeof(__uint8_t):
+               free(nlinks.un8);
+               break;
+       case sizeof(__uint16_t):
+               free(nlinks.un16);
+               break;
+       case sizeof(__uint32_t):
+               free(nlinks.un32);
+               break;
+       default:
+               ASSERT(0);
+       }
+}
+
+static void
 free_ino_tree_node(
        struct ino_tree_node    *irec)
 {
@@ -269,11 +272,12 @@ free_ino_tree_node(
        irec->avl_node.avl_forw = NULL;
        irec->avl_node.avl_back = NULL;
 
-       free(irec->disk_nlinks);
+       free_nlink_array(irec->disk_nlinks, irec->nlink_size);
        if (irec->ino_un.ex_data != NULL)  {
                if (full_ino_ex_data) {
                        free(irec->ino_un.ex_data->parents);
-                       free(irec->ino_un.ex_data->counted_nlinks);
+                       free_nlink_array(irec->ino_un.ex_data->counted_nlinks,
+                                        irec->nlink_size);
                }
                free(irec->ino_un.ex_data);
 
@@ -707,10 +711,23 @@ alloc_ex_data(ino_tree_node_t *irec)
                do_error(_("could not malloc inode extra data\n"));
 
        irec->ino_un.ex_data->parents = ptbl;
-       irec->ino_un.ex_data->counted_nlinks = calloc(1, 
irec->nlinkops->nlink_size);
 
-       if (irec->ino_un.ex_data->counted_nlinks == NULL)
-               do_error(_("could not malloc inode extra data\n"));
+       switch (irec->nlink_size) {
+       case sizeof(__uint8_t):
+               irec->ino_un.ex_data->counted_nlinks.un8 =
+                       alloc_nlink_array(irec->nlink_size);
+               break;
+       case sizeof(__uint16_t):
+               irec->ino_un.ex_data->counted_nlinks.un16 =
+                       alloc_nlink_array(irec->nlink_size);
+               break;
+       case sizeof(__uint32_t):
+               irec->ino_un.ex_data->counted_nlinks.un32 =
+                       alloc_nlink_array(irec->nlink_size);
+               break;
+       default:
+               ASSERT(0);
+       }
 }
 
 void

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