tmpfs: remove_shmem_readpage

Remove that pernicious shmem_readpage() at last: the things we needed it
for (splice, loop, sendfile, i915 GEM) are now fully taken care of by
shmem_file_splice_read() and shmem_read_mapping_page_gfp().

This removal clears the way for a simpler shmem_getpage_gfp(), since page
is never passed in; but leave most of that cleanup until after.

sys_readahead() and sys_fadvise(POSIX_FADV_WILLNEED) will now EINVAL,
instead of unexpectedly trying to read ahead on tmpfs: if that proves to
be an issue for someone, then we can either arrange for them to return
success instead, or try to implement async readahead on tmpfs.

Signed-off-by: Hugh Dickins <hughd@google.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 f6c94ba..ff6713a 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1246,7 +1246,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t idx,
        struct address_space *mapping = inode->i_mapping;
        struct shmem_inode_info *info = SHMEM_I(inode);
        struct shmem_sb_info *sbinfo;
-       struct page *filepage = *pagep;
+       struct page *filepage;
        struct page *swappage;
        struct page *prealloc_page = NULL;
        swp_entry_t *entry;
@@ -1255,18 +1255,8 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t idx,
 
        if (idx >= SHMEM_MAX_INDEX)
                return -EFBIG;
-
-       /*
-        * Normally, filepage is NULL on entry, and either found
-        * uptodate immediately, or allocated and zeroed, or read
-        * in under swappage, which is then assigned to filepage.
-        * But shmem_readpage (required for splice) passes in a locked
-        * filepage, which may be found not uptodate by other callers
-        * too, and may need to be copied from the swappage read in.
-        */
 repeat:
-       if (!filepage)
-               filepage = find_lock_page(mapping, idx);
+       filepage = find_lock_page(mapping, idx);
        if (filepage && PageUptodate(filepage))
                goto done;
        if (!filepage) {
@@ -1513,8 +1503,7 @@ nospace:
         * Perhaps the page was brought in from swap between find_lock_page
         * and taking info->lock?  We allow for that at add_to_page_cache_lru,
         * but must also avoid reporting a spurious ENOSPC while working on a
-        * full tmpfs.  (When filepage has been passed in to shmem_getpage, it
-        * is already in page cache, which prevents this race from occurring.)
+        * full tmpfs.
         */
        if (!filepage) {
                struct page *page = find_get_page(mapping, idx);
@@ -1527,7 +1516,7 @@ nospace:
        spin_unlock(&info->lock);
        error = -ENOSPC;
 failed:
-       if (*pagep != filepage) {
+       if (filepage) {
                unlock_page(filepage);
                page_cache_release(filepage);
        }
@@ -1673,19 +1662,6 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
 static const struct inode_operations shmem_symlink_inode_operations;
 static const struct inode_operations shmem_symlink_inline_operations;
 
-/*
- * Normally tmpfs avoids the use of shmem_readpage and shmem_write_begin;
- * but providing them allows a tmpfs file to be used for splice, sendfile, and
- * below the loop driver, in the generic fashion that many filesystems support.
- */
-static int shmem_readpage(struct file *file, struct page *page)
-{
-       struct inode *inode = page->mapping->host;
-       int error = shmem_getpage(inode, page->index, &page, SGP_CACHE, NULL);
-       unlock_page(page);
-       return error;
-}
-
 static int
 shmem_write_begin(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned flags,
@@ -1693,7 +1669,6 @@ shmem_write_begin(struct file *file, struct address_space *mapping,
 {
        struct inode *inode = mapping->host;
        pgoff_t index = pos >> PAGE_CACHE_SHIFT;
-       *pagep = NULL;
        return shmem_getpage(inode, index, pagep, SGP_WRITE, NULL);
 }
 
@@ -1893,7 +1868,6 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
        error = 0;
 
        while (spd.nr_pages < nr_pages) {
-               page = NULL;
                error = shmem_getpage(inode, index, &page, SGP_CACHE, NULL);
                if (error)
                        break;
@@ -1916,7 +1890,6 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos,
                page = spd.pages[page_nr];
 
                if (!PageUptodate(page) || page->mapping != mapping) {
-                       page = NULL;
                        error = shmem_getpage(inode, index, &page,
                                                        SGP_CACHE, NULL);
                        if (error)
@@ -2125,7 +2098,7 @@ static int shmem_symlink(struct inode *dir, struct dentry *dentry, const char *s
        int error;
        int len;
        struct inode *inode;
-       struct page *page = NULL;
+       struct page *page;
        char *kaddr;
        struct shmem_inode_info *info;
 
@@ -2803,7 +2776,6 @@ static const struct address_space_operations shmem_aops = {
        .writepage      = shmem_writepage,
        .set_page_dirty = __set_page_dirty_no_writeback,
 #ifdef CONFIG_TMPFS
-       .readpage       = shmem_readpage,
        .write_begin    = shmem_write_begin,
        .write_end      = shmem_write_end,
 #endif
@@ -3175,7 +3147,7 @@ struct page *shmem_read_mapping_page_gfp(struct address_space *mapping,
 {
 #ifdef CONFIG_SHMEM
        struct inode *inode = mapping->host;
-       struct page *page = NULL;
+       struct page *page;
        int error;
 
        BUG_ON(mapping->a_ops != &shmem_aops);