ext4: fix ext4_da_block_invalidatepages() to handle page range properly

If ext4_da_block_invalidatepages() is called because of a
failure from ext4_map_blocks() in mpage_da_map_and_submit(),
it's supposed to clean up -- including unlock -- all the
pages in the mpd structure.  But these values may not match
up, even on a system in which block size == page size:

   mpd->b_blocknr != mpd->first_page
   mpd->b_size != (mpd->next_page - mpd->first_page)

ext4_da_block_invalidatepages() has been using b_blocknr and
b_size; this patch changes it to use first_page and
next_page.

Tested:  I injected a small number (5%) of failures in
ext4_map_blocks() in the case that the flags contain
EXT4_GET_BLOCKS_DELALLOC_RESERVE, and ran fsstress on this
kernel.  Without this patch, I got hung tasks every time.
With this patch, I see no hangs in many runs of fsstress.

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 4 insertions, 7 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index fd369dbce6af..e878c3a7aaf0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2165,8 +2165,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd,
         return ret;
 }
 
-static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
-                                        sector_t logical, long blk_cnt)
+static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd)
 {
         int nr_pages, i;
         pgoff_t index, end;
@@ -2174,9 +2173,8 @@ static void ext4_da_block_invalidatepages(struct mpage_da_data *mpd,
         struct inode *inode = mpd->inode;
         struct address_space *mapping = inode->i_mapping;
 
-        index = logical >> (PAGE_CACHE_SHIFT - inode->i_blkbits);
-        end   = (logical + blk_cnt - 1) >>
-                                (PAGE_CACHE_SHIFT - inode->i_blkbits);
+        index = mpd->first_page;
+        end   = mpd->next_page - 1;
         while (index <= end) {
                 nr_pages = pagevec_lookup(&pvec, mapping, index, PAGEVEC_SIZE);
                 if (nr_pages == 0)
@@ -2312,8 +2310,7 @@ static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
                                 ext4_print_free_blocks(mpd->inode);
                 }
                 /* invalidate all the pages */
-                ext4_da_block_invalidatepages(mpd, next,
-                                mpd->b_size >> mpd->inode->i_blkbits);
+                ext4_da_block_invalidatepages(mpd);
 
                 /* Mark this page range as having been completed */
                 mpd->io_done = 1;