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Message-ID: <alpine.LSU.2.00.1106091534470.2200@sister.anvils>
Date: Thu, 9 Jun 2011 15:35:42 -0700 (PDT)
From: Hugh Dickins <hughd@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 4/7] 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@...gle.com>
---
mm/shmem.c | 40 ++++++----------------------------------
1 file changed, 6 insertions(+), 34 deletions(-)
--- linux.orig/mm/shmem.c 2011-06-09 11:38:22.912896122 -0700
+++ linux/mm/shmem.c 2011-06-09 11:39:32.361240481 -0700
@@ -1246,7 +1246,7 @@ static int shmem_getpage_gfp(struct inod
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 inod
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(str
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, str
{
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(st
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(st
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 *d
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_operat
.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
{
#ifdef CONFIG_SHMEM
struct inode *inode = mapping->host;
- struct page *page = NULL;
+ struct page *page;
int error;
BUG_ON(mapping->a_ops != &shmem_aops);
--
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