[Patch] shmem fixes for 2.4.1-pre7

[Christoph Rohland]

Hi Linus,

Here is a patch against 2.4.1-pre7 which

1) Adds prototype for shmem_lock to mm.h
2) Again brings the fixes for the accounting. I still think it
   should be applied.

Greetings
                Christoph

diff -uNr 1-pre7/include/linux/mm.h m1-pre7/include/linux/mm.h
--- 1-pre7/include/linux/mm.h   Tue Jan 16 09:33:02 2001
+++ m1-pre7/include/linux/mm.h  Tue Jan 16 09:34:20 2001
@@ -386,6 +386,7 @@
 
 struct page * shmem_nopage(struct vm_area_struct * vma, unsigned long address, int 
no_share);
 struct file *shmem_file_setup(char * name, loff_t size);
+void shmem_lock(struct file * file, int lock);
 extern int shmem_zero_setup(struct vm_area_struct *);
 
 extern void zap_page_range(struct mm_struct *mm, unsigned long address, unsigned long 
size);
diff -uNr 1-pre7/mm/shmem.c m1-pre7/mm/shmem.c
--- 1-pre7/mm/shmem.c   Tue Jan 16 09:33:02 2001
+++ m1-pre7/mm/shmem.c  Tue Jan 16 09:33:45 2001
@@ -117,11 +117,43 @@
        return 0;
 }
 
+/*
+ * shmem_recalc_inode - recalculate the size of an inode
+ *
+ * @inode: inode to recalc
+ *
+ * We have to calculate the free blocks since the mm can drop pages
+ * behind our back
+ *
+ * But we know that normally
+ * inodes->i_blocks == inode->i_mapping->nrpages + info->swapped
+ *
+ * So the mm freed 
+ * inodes->i_blocks - (inode->i_mapping->nrpages + info->swapped)
+ *
+ * It has to be called with the spinlock held.
+ */
+
+static void shmem_recalc_inode(struct inode * inode)
+{
+       unsigned long freed;
+
+       freed = inode->i_blocks -
+               (inode->i_mapping->nrpages + inode->u.shmem_i.swapped);
+       if (freed){
+               struct shmem_sb_info * info = &inode->i_sb->u.shmem_sb;
+               inode->i_blocks -= freed;
+               spin_lock (&info->stat_lock);
+               info->free_blocks += freed;
+               spin_unlock (&info->stat_lock);
+       }
+}
+
 static void shmem_truncate (struct inode * inode)
 {
        int clear_base;
        unsigned long start;
-       unsigned long mmfreed, freed = 0;
+       unsigned long freed = 0;
        swp_entry_t **base, **ptr;
        struct shmem_inode_info * info = &inode->u.shmem_i;
 
@@ -154,26 +186,9 @@
        info->i_indirect = 0;
 
 out:
-
-       /*
-        * We have to calculate the free blocks since we do not know
-        * how many pages the mm discarded
-        *
-        * But we know that normally
-        * inodes->i_blocks == inode->i_mapping->nrpages + info->swapped
-        *
-        * So the mm freed 
-        * inodes->i_blocks - (inode->i_mapping->nrpages + info->swapped)
-        */
-
-       mmfreed = inode->i_blocks - (inode->i_mapping->nrpages + info->swapped);
        info->swapped -= freed;
-       inode->i_blocks -= freed + mmfreed;
+       shmem_recalc_inode(inode);
        spin_unlock (&info->lock);
-
-       spin_lock (&inode->i_sb->u.shmem_sb.stat_lock);
-       inode->i_sb->u.shmem_sb.free_blocks += freed + mmfreed;
-       spin_unlock (&inode->i_sb->u.shmem_sb.stat_lock);
 }
 
 static void shmem_delete_inode(struct inode * inode)
@@ -208,6 +223,7 @@
                return 1;
 
        spin_lock(&info->lock);
+       shmem_recalc_inode(page->mapping->host);
        entry = shmem_swp_entry (info, page->index);
        if (!entry)     /* this had been allocted on page allocation */
                BUG();
@@ -269,6 +285,9 @@
        entry = shmem_swp_entry (info, idx);
        if (!entry)
                goto oom;
+       spin_lock (&info->lock);
+       shmem_recalc_inode(inode);
+       spin_unlock (&info->lock);
        if (entry->val) {
                unsigned long flags;
 
-
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