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Subject[PATCH] reiserfs highmem bug on tail reads

Ok, so all the reiserfs tail bugs weren't quite fixed yet, the last
tail fix can cause problems with highmem turned on. Both bugs are
in fs/reiserfs/inode.c:_get_block_create_0

When reading the tail in, if the buffer was already up to date,
we skip the disk i/o and return. But the cleanup code assumes the
page was kmap'd, which isn't right.

Also, there was a chance to double kmap the page if kmap scheduled a
nd the tree balanced while we slept. This bug has been there for
a long time.

Anyway, this was tested with Andrea's HIGHMEM_DEBUG_MERE_MORTALS
patch to force highmem on my 128MB machine. It works for me, but
more testers are always good.

-chris

against 2.4.4-pre6, should work against 2.4.3 or higher.

diff -Nru a/fs/reiserfs/inode.c b/fs/reiserfs/inode.c
--- a/fs/reiserfs/inode.c Wed Apr 25 23:15:14 2001
+++ b/fs/reiserfs/inode.c Wed Apr 25 23:15:14 2001
@@ -374,9 +374,11 @@
** sure we need to. But, this means the item might move if
** kmap schedules
*/
- p = (char *)kmap(bh_result->b_page) ;
- if (fs_changed (fs_gen, inode->i_sb) && item_moved (&tmp_ih, &path)) {
- goto research;
+ if (!p) {
+ p = (char *)kmap(bh_result->b_page) ;
+ if (fs_changed (fs_gen, inode->i_sb) && item_moved (&tmp_ih, &path)) {
+ goto research;
+ }
}
p += offset ;
memset (p, 0, inode->i_sb->s_blocksize);
@@ -420,14 +422,15 @@
ih = get_ih (&path);
} while (1);

+ flush_dcache_page(bh_result->b_page) ;
+ kunmap(bh_result->b_page) ;
+
finished:
pathrelse (&path);
bh_result->b_blocknr = 0 ;
bh_result->b_dev = inode->i_dev;
mark_buffer_uptodate (bh_result, 1);
bh_result->b_state |= (1UL << BH_Mapped);
- flush_dcache_page(bh_result->b_page) ;
- kunmap(bh_result->b_page) ;
return 0;
}





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