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>

1 files changed, 1 insertions, 93 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 4ce02e0673db..3f696f7d9bac 100644
--- 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,