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Date: Sat, 28 Jun 2008 15:48:55 +0530
From: "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To: cmm@...ibm.com, tytso@....edu, sandeen@...hat.com, jack@...e.cz
Cc: linux-ext4@...r.kernel.org,
"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH] ext4: Handle page without buffers in ext4_*_writepage()
From: Jan Kara <jack@...e.cz>
It can happen that buffers are removed from the page before it gets
marked dirty and then is passed to writepage(). Make ext4_*_writepage()
handle this case (basically by just skipping some checks in this case).
Signed-off-by: Jan Kara <jack@...e.cz>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
fs/ext4/inode.c | 86 +++++++++++++++++++++++++++++++++++++++++++++---------
1 files changed, 71 insertions(+), 15 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 10f1d5d..8bd2595 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1592,11 +1592,15 @@ static int ext4_da_get_block_write(struct inode *inode, sector_t iblock,
handle_t *handle = NULL;
handle = ext4_journal_current_handle();
- BUG_ON(handle == NULL);
- BUG_ON(create == 0);
-
- ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
+ if (!handle) {
+ ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
+ bh_result, 0, 0, 0);
+ BUG_ON(!ret);
+ } else {
+ ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
bh_result, create, 0, EXT4_DELALLOC_RSVED);
+ }
+
if (ret > 0) {
bh_result->b_size = (ret << inode->i_blkbits);
@@ -1655,7 +1659,13 @@ static int ext4_da_writepage(struct page *page,
struct inode *inode = page->mapping->host;
handle = ext4_journal_current_handle();
- if (!handle) {
+ /* The test for page_has_buffers() is subtle:
+ * We know the page is dirty but it lost buffers. That means that
+ * at some moment in time after write_begin() / write_end() has been
+ * called all buffers have been clean and thus they must have been
+ * written at least once. So they are all mapped and we can happily
+ * proceed with mapping them and writing the page. */
+ if (!handle && page_has_buffers(page)) {
/*
* This can happen when we aren't called via
* ext4_da_writepages() but directly (shrink_page_list).
@@ -1918,6 +1928,28 @@ static int bput_one(handle_t *handle, struct buffer_head *bh)
return 0;
}
+static int ext4_normal_get_block_write(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh_result, int create)
+{
+ int ret = 0;
+ handle_t *handle = ext4_journal_current_handle();
+ unsigned max_blocks = bh_result->b_size >> inode->i_blkbits;
+
+ if (!handle) {
+ ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
+ bh_result, 0, 0, 0);
+ BUG_ON(!ret);
+ } else {
+ ret = ext4_get_blocks_wrap(handle, inode, iblock, max_blocks,
+ bh_result, create, 0, EXT4_DELALLOC_RSVED);
+ }
+ if (ret > 0) {
+ bh_result->b_size = (ret << inode->i_blkbits);
+ ret = 0;
+ }
+ return ret;
+}
+
/*
* Note that we don't need to start a transaction unless we're journaling data
* because we should have holes filled from ext4_page_mkwrite(). We even don't
@@ -1977,12 +2009,13 @@ static int __ext4_normal_writepage(struct page *page,
struct inode *inode = page->mapping->host;
if (test_opt(inode->i_sb, NOBH))
- return nobh_writepage(page, ext4_get_block, wbc);
+ return nobh_writepage(page,
+ ext4_normal_get_block_write, wbc);
else
- return block_write_full_page(page, ext4_get_block, wbc);
+ return block_write_full_page(page,
+ ext4_normal_get_block_write, wbc);
}
-
static int ext4_normal_writepage(struct page *page,
struct writeback_control *wbc)
{
@@ -1991,13 +2024,24 @@ static int ext4_normal_writepage(struct page *page,
loff_t len;
J_ASSERT(PageLocked(page));
- J_ASSERT(page_has_buffers(page));
if (page->index == size >> PAGE_CACHE_SHIFT)
len = size & ~PAGE_CACHE_MASK;
else
len = PAGE_CACHE_SIZE;
- BUG_ON(walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
- ext4_bh_unmapped_or_delay));
+
+ if (page_has_buffers(page)) {
+ /* if page has buffers it should all be mapped
+ * and allocated. If there are not buffers attached
+ * to the page we know the page is dirty but it lost
+ * buffers. That means that at some moment in time
+ * after write_begin() / write_end() has been called
+ * all buffers have been clean and thus they must have been
+ * written at least once. So they are all mapped and we can
+ * happily proceed with mapping them and writing the page.
+ */
+ BUG_ON(walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
+ ext4_bh_unmapped_or_delay));
+ }
if (!ext4_journal_current_handle())
return __ext4_normal_writepage(page, wbc);
@@ -2017,7 +2061,8 @@ static int __ext4_journalled_writepage(struct page *page,
int ret = 0;
int err;
- ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE, ext4_get_block);
+ ret = block_prepare_write(page, 0, PAGE_CACHE_SIZE,
+ ext4_normal_get_block_write);
if (ret != 0)
goto out_unlock;
@@ -2064,13 +2109,24 @@ static int ext4_journalled_writepage(struct page *page,
loff_t len;
J_ASSERT(PageLocked(page));
- J_ASSERT(page_has_buffers(page));
if (page->index == size >> PAGE_CACHE_SHIFT)
len = size & ~PAGE_CACHE_MASK;
else
len = PAGE_CACHE_SIZE;
- BUG_ON(walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
- ext4_bh_unmapped_or_delay));
+
+ if (page_has_buffers(page)) {
+ /* if page has buffers it should all be mapped
+ * and allocated. If there are not buffers attached
+ * to the page we know the page is dirty but it lost
+ * buffers. That means that at some moment in time
+ * after write_begin() / write_end() has been called
+ * all buffers have been clean and thus they must have been
+ * written at least once. So they are all mapped and we can
+ * happily proceed with mapping them and writing the page.
+ */
+ BUG_ON(walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
+ ext4_bh_unmapped_or_delay));
+ }
if (ext4_journal_current_handle())
goto no_write;
--
1.5.6.1.78.gde8d9.dirty
--
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