tmpfs: revert SEEK_DATA and SEEK_HOLE

Revert 4fb5ef089b28 ("tmpfs: support SEEK_DATA and SEEK_HOLE").  I believe
it's correct, and it's been nice to have from rc1 to rc6; but as the
original commit said:

I don't know who actually uses SEEK_DATA or SEEK_HOLE, and whether it
would be of any use to them on tmpfs.  This code adds 92 lines and 752
bytes on x86_64 - is that bloat or worthwhile?

Nobody asked for it, so I conclude that it's bloat: let's revert tmpfs to
the dumb generic support for v3.5.  We can always reinstate it later if
useful, and anyone needing it in a hurry can just get it out of git.

Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Josef Bacik <josef@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andreas Dilger <adilger@dilger.ca>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Marco Stornelli <marco.stornelli@gmail.com>
Cc: Jeff liu <jeff.liu@oracle.com>
Cc: Chris Mason <chris.mason@fusionio.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index 4ce02e0673db612befb63def38911d2d2b0638af..3f696f7d9bace4279c033dff173cdfd9f0c3f03b 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1692,98 +1692,6 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
        return error;
 }
 
-/*
- * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
- */
-static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
-                                   pgoff_t index, pgoff_t end, int origin)
-{
-       struct page *page;
-       struct pagevec pvec;
-       pgoff_t indices[PAGEVEC_SIZE];
-       bool done = false;
-       int i;
-
-       pagevec_init(&pvec, 0);
-       pvec.nr = 1;            /* start small: we may be there already */
-       while (!done) {
-               pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
-                                       pvec.nr, pvec.pages, indices);
-               if (!pvec.nr) {
-                       if (origin == SEEK_DATA)
-                               index = end;
-                       break;
-               }
-               for (i = 0; i < pvec.nr; i++, index++) {
-                       if (index < indices[i]) {
-                               if (origin == SEEK_HOLE) {
-                                       done = true;
-                                       break;
-                               }
-                               index = indices[i];
-                       }
-                       page = pvec.pages[i];
-                       if (page && !radix_tree_exceptional_entry(page)) {
-                               if (!PageUptodate(page))
-                                       page = NULL;
-                       }
-                       if (index >= end ||
-                           (page && origin == SEEK_DATA) ||
-                           (!page && origin == SEEK_HOLE)) {
-                               done = true;
-                               break;
-                       }
-               }
-               shmem_deswap_pagevec(&pvec);
-               pagevec_release(&pvec);
-               pvec.nr = PAGEVEC_SIZE;
-               cond_resched();
-       }
-       return index;
-}
-
-static loff_t shmem_file_llseek(struct file *file, loff_t offset, int origin)
-{
-       struct address_space *mapping;
-       struct inode *inode;
-       pgoff_t start, end;
-       loff_t new_offset;
-
-       if (origin != SEEK_DATA && origin != SEEK_HOLE)
-               return generic_file_llseek_size(file, offset, origin,
-                                                       MAX_LFS_FILESIZE);
-       mapping = file->f_mapping;
-       inode = mapping->host;
-       mutex_lock(&inode->i_mutex);
-       /* We're holding i_mutex so we can access i_size directly */
-
-       if (offset < 0)
-               offset = -EINVAL;
-       else if (offset >= inode->i_size)
-               offset = -ENXIO;
-       else {
-               start = offset >> PAGE_CACHE_SHIFT;
-               end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
-               new_offset = shmem_seek_hole_data(mapping, start, end, origin);
-               new_offset <<= PAGE_CACHE_SHIFT;
-               if (new_offset > offset) {
-                       if (new_offset < inode->i_size)
-                               offset = new_offset;
-                       else if (origin == SEEK_DATA)
-                               offset = -ENXIO;
-                       else
-                               offset = inode->i_size;
-               }
-       }
-
-       if (offset >= 0 && offset != file->f_pos) {
-               file->f_pos = offset;
-               file->f_version = 0;
-       }
-       mutex_unlock(&inode->i_mutex);
-       return offset;
-}
-
 static long shmem_fallocate(struct file *file, int mode, loff_t offset,
                                                         loff_t len)
 {
@@ -2787,7 +2695,7 @@ static const struct address_space_operations shmem_aops = {
 static const struct file_operations shmem_file_operations = {
        .mmap           = shmem_mmap,
 #ifdef CONFIG_TMPFS
-       .llseek         = shmem_file_llseek,
+       .llseek         = generic_file_llseek,
        .read           = do_sync_read,
        .write          = do_sync_write,
        .aio_read       = shmem_file_aio_read,