[PATCH] [2.5] reiserfs: fix races between link and unlink on same file

From: Oleg Drokin (green@namesys.com)
Date: Thu Jul 31 2003 - 09:42:04 EST

Hello!

    This patch (originally by Chris Mason) fixes link/unlink races in reiserfs.
    The patch is against 2.6.0-test2, please apply.

===== fs/reiserfs/namei.c 1.47 vs edited =====
--- 1.47/fs/reiserfs/namei.c Mon Jun 30 10:49:04 2003
+++ edited/fs/reiserfs/namei.c Thu Jul 31 18:01:55 2003
@@ -822,6 +822,7 @@
     int windex ;
     struct reiserfs_transaction_handle th ;
     int jbegin_count;
+ unsigned long savelink;
 
     inode = dentry->d_inode;
 
@@ -858,11 +859,20 @@
         inode->i_nlink = 1;
     }
 
+ inode->i_nlink--;
+
+ /*
+ * we schedule before doing the add_save_link call, save the link
+ * count so we don't race
+ */
+ savelink = inode->i_nlink;
+
+
     retval = reiserfs_cut_from_item (&th, &path, &(de.de_entry_key), dir, NULL, 0);
- if (retval < 0)
+ if (retval < 0) {
+ inode->i_nlink++;
         goto end_unlink;
-
- inode->i_nlink--;
+ }
     inode->i_ctime = CURRENT_TIME;
     reiserfs_update_sd (&th, inode);
 
@@ -871,7 +881,7 @@
     dir->i_ctime = dir->i_mtime = CURRENT_TIME;
     reiserfs_update_sd (&th, dir);
 
- if (!inode->i_nlink)
+ if (!savelink)
        /* prevent file from getting lost */
        add_save_link (&th, inode, 0/* not truncate */);
 
@@ -976,6 +986,12 @@
         reiserfs_write_unlock(dir->i_sb);
         return -EMLINK;
     }
+ if (inode->i_nlink == 0) {
+ return -ENOENT;
+ }
+
+ /* inc before scheduling so reiserfs_unlink knows we are here */
+ inode->i_nlink++;
 
     journal_begin(&th, dir->i_sb, jbegin_count) ;
     windex = push_journal_writer("reiserfs_link") ;
@@ -988,13 +1004,13 @@
     reiserfs_update_inode_transaction(dir) ;
 
     if (retval) {
+ inode->i_nlink--;
         pop_journal_writer(windex) ;
         journal_end(&th, dir->i_sb, jbegin_count) ;
         reiserfs_write_unlock(dir->i_sb);
         return retval;
     }
 
- inode->i_nlink++;
     inode->i_ctime = CURRENT_TIME;
     reiserfs_update_sd (&th, inode);
 
@@ -1068,6 +1084,7 @@
     struct reiserfs_transaction_handle th ;
     int jbegin_count ;
     umode_t old_inode_mode;
+ unsigned long savelink = 1;
 
     /* two balancings: old name removal, new name insertion or "save" link,
        stat data updates: old directory and new directory and maybe block
@@ -1246,6 +1263,7 @@
             new_dentry_inode->i_nlink--;
         }
         new_dentry_inode->i_ctime = new_dir->i_ctime;
+ savelink = new_dentry_inode->i_nlink;
     }
 
     if (S_ISDIR(old_inode_mode)) {
@@ -1279,7 +1297,7 @@
     reiserfs_update_sd (&th, new_dir);
 
     if (new_dentry_inode) {
- if (new_dentry_inode->i_nlink == 0)
+ if (savelink == 0)
             add_save_link (&th, new_dentry_inode, 0/* not truncate */);
         reiserfs_update_sd (&th, new_dentry_inode);
     }
-
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This archive was generated by hypermail 2b29 : Thu Jul 31 2003 - 22:00:50 EST