Restructure zfs_readdir() to fix regressions

This does the following:

1. It creates a uint8_t type value, which is initialized to DT_DIR on
dot directories and ZFS_DIRENT_TYPE(zap.za_first_integer) otherwise.
This resolves a regression where we return unintialized values as the
directory entry type on dot directories. This was accidentally
introduced by commit 8170d281263e52ff33d7fba93ab625196844df36.

2. It restructures zfs_readdir() code to use `uint64_t offset` like
Illumos instead of `loff_t *pos`. This resolves a regression where
negative ZAP cursors were treated as if they were dot directories.

3. It restructures the function to more closely match the structure of
zfs_readdir() on Illumos and removes the unused variable outcount, which
was only used on Illumos.

Signed-off-by: Richard Yao <ryao@gentoo.org>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1750

diff --git a/module/zfs/zfs_vnops.c b/module/zfs/zfs_vnops.c
index 876d44b3563dae38e3989c632c356d2b7b9637b1..436a25eaf844ca75f203c19bd1973edbf3a4055f 100644 (file)
--- a/module/zfs/zfs_vnops.c
+++ b/module/zfs/zfs_vnops.c
@@ -2004,12 +2004,12 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
        objset_t        *os;
        zap_cursor_t    zc;
        zap_attribute_t zap;
-       int             outcount;
        int             error;
        uint8_t         prefetch;
+       uint8_t         type;
        int             done = 0;
        uint64_t        parent;
-       loff_t          *pos = &(ctx->pos);
+       uint64_t        offset; /* must be unsigned; checks for < 1 */
 
        ZFS_ENTER(zsb);
        ZFS_VERIFY_ZP(zp);
@@ -2021,17 +2021,18 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
        /*
         * Quit if directory has been removed (posix)
         */
-       error = 0;
        if (zp->z_unlinked)
                goto out;
 
+       error = 0;
        os = zsb->z_os;
+       offset = ctx->pos;
        prefetch = zp->z_zn_prefetch;
 
        /*
         * Initialize the iterator cursor.
         */
-       if (*pos <= 3) {
+       if (offset <= 3) {
                /*
                 * Start iteration from the beginning of the directory.
                 */
@@ -2040,31 +2041,32 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
                /*
                 * The offset is a serialized cursor.
                 */
-               zap_cursor_init_serialized(&zc, os, zp->z_id, *pos);
+               zap_cursor_init_serialized(&zc, os, zp->z_id, offset);
        }
 
        /*
         * Transform to file-system independent format
         */
-       outcount = 0;
-
        while (!done) {
                uint64_t objnum;
                /*
                 * Special case `.', `..', and `.zfs'.
                 */
-               if (*pos == 0) {
+               if (offset == 0) {
                        (void) strcpy(zap.za_name, ".");
                        zap.za_normalization_conflict = 0;
                        objnum = zp->z_id;
-               } else if (*pos == 1) {
+                       type = DT_DIR;
+               } else if (offset == 1) {
                        (void) strcpy(zap.za_name, "..");
                        zap.za_normalization_conflict = 0;
                        objnum = parent;
-               } else if (*pos == 2 && zfs_show_ctldir(zp)) {
+                       type = DT_DIR;
+               } else if (offset == 2 && zfs_show_ctldir(zp)) {
                        (void) strcpy(zap.za_name, ZFS_CTLDIR_NAME);
                        zap.za_normalization_conflict = 0;
                        objnum = ZFSCTL_INO_ROOT;
+                       type = DT_DIR;
                } else {
                        /*
                         * Grab next entry.
@@ -2089,7 +2091,7 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
                                    "entry, obj = %lld, offset = %lld, "
                                    "length = %d, num = %lld\n",
                                    (u_longlong_t)zp->z_id,
-                                   (u_longlong_t)*pos,
+                                   (u_longlong_t)offset,
                                    zap.za_integer_length,
                                    (u_longlong_t)zap.za_num_integers);
                                error = ENXIO;
@@ -2097,10 +2099,11 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
                        }
 
                        objnum = ZFS_DIRENT_OBJ(zap.za_first_integer);
+                       type = ZFS_DIRENT_TYPE(zap.za_first_integer);
                }
 
                done = !dir_emit(ctx, zap.za_name, strlen(zap.za_name),
-                   objnum, ZFS_DIRENT_TYPE(zap.za_first_integer));
+                   objnum, type);
                if (done)
                        break;
 
@@ -2109,12 +2112,16 @@ zfs_readdir(struct inode *ip, struct dir_context *ctx, cred_t *cr)
                        dmu_prefetch(os, objnum, 0, 0);
                }
 
-               if (*pos > 2 || (*pos == 2 && !zfs_show_ctldir(zp))) {
+               /*
+                * Move to the next entry, fill in the previous offset.
+                */
+               if (offset > 2 || (offset == 2 && !zfs_show_ctldir(zp))) {
                        zap_cursor_advance(&zc);
-                       *pos = zap_cursor_serialize(&zc);
+                       offset = zap_cursor_serialize(&zc);
                } else {
-                       (*pos)++;
+                       offset += 1;
                }
+               ctx->pos = offset;
        }
        zp->z_zn_prefetch = B_FALSE; /* a lookup will re-enable pre-fetching */