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Message-Id: <1287761366-20249-2-git-send-email-tytso@mit.edu>
Date: Fri, 22 Oct 2010 11:29:21 -0400
From: Theodore Ts'o <tytso@....edu>
To: Ext4 Developers List <linux-ext4@...r.kernel.org>
Cc: Theodore Ts'o <tytso@....edu>
Subject: [PATCH 1/6] ext4: call mpage_da_submit_io() from mpage_da_map_blocks()
Eventually we need to completely reorganize the ext4 writepage
callpath, but for now, we simplify things a little by calling
mpage_da_submit_io() from mpage_da_map_blocks(), since all of the
places where we call mpage_da_map_blocks() it is followed up by a call
to mpage_da_submit_io().
We're also a wee bit better with respect to error handling, but there
are still a number of issues where it's not clear what the right thing
is to do with ext4 functions deep in the writeback codepath fails.
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
---
fs/ext4/inode.c | 63 ++++++++++++++++++++++++++----------------------------
1 files changed, 30 insertions(+), 33 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 670ab15..c3cc036 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -60,6 +60,7 @@ static inline int ext4_begin_ordered_truncate(struct inode *inode,
}
static void ext4_invalidatepage(struct page *page, unsigned long offset);
+static int ext4_writepage(struct page *page, struct writeback_control *wbc);
/*
* Test whether an inode is a fast symlink.
@@ -2033,7 +2034,7 @@ static int mpage_da_submit_io(struct mpage_da_data *mpd)
BUG_ON(PageWriteback(page));
pages_skipped = mpd->wbc->pages_skipped;
- err = mapping->a_ops->writepage(page, mpd->wbc);
+ err = ext4_writepage(page, mpd->wbc);
if (!err && (pages_skipped == mpd->wbc->pages_skipped))
/*
* have successfully written the page
@@ -2189,14 +2190,15 @@ static void ext4_print_free_blocks(struct inode *inode)
}
/*
- * mpage_da_map_blocks - go through given space
+ * mpage_da_map_and_submit - go through given space, map them
+ * if necessary, and then submit them for I/O
*
* @mpd - bh describing space
*
* The function skips space we know is already mapped to disk blocks.
*
*/
-static int mpage_da_map_blocks(struct mpage_da_data *mpd)
+static void mpage_da_map_and_submit(struct mpage_da_data *mpd)
{
int err, blks, get_blocks_flags;
struct ext4_map_blocks map;
@@ -2206,18 +2208,14 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
handle_t *handle = NULL;
/*
- * We consider only non-mapped and non-allocated blocks
+ * If the blocks are mapped already, or we couldn't accumulate
+ * any blocks, then proceed immediately to the submission stage.
*/
- if ((mpd->b_state & (1 << BH_Mapped)) &&
- !(mpd->b_state & (1 << BH_Delay)) &&
- !(mpd->b_state & (1 << BH_Unwritten)))
- return 0;
-
- /*
- * If we didn't accumulate anything to write simply return
- */
- if (!mpd->b_size)
- return 0;
+ if ((mpd->b_size == 0) ||
+ ((mpd->b_state & (1 << BH_Mapped)) &&
+ !(mpd->b_state & (1 << BH_Delay)) &&
+ !(mpd->b_state & (1 << BH_Unwritten))))
+ goto submit_io;
handle = ext4_journal_current_handle();
BUG_ON(!handle);
@@ -2254,17 +2252,18 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
err = blks;
/*
- * If get block returns with error we simply
- * return. Later writepage will redirty the page and
- * writepages will find the dirty page again
+ * If get block returns EAGAIN or ENOSPC and there
+ * appears to be free blocks we will call
+ * ext4_writepage() for all of the pages which will
+ * just redirty the pages.
*/
if (err == -EAGAIN)
- return 0;
+ goto submit_io;
if (err == -ENOSPC &&
ext4_count_free_blocks(sb)) {
mpd->retval = err;
- return 0;
+ goto submit_io;
}
/*
@@ -2289,7 +2288,7 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
/* invalidate all the pages */
ext4_da_block_invalidatepages(mpd, next,
mpd->b_size >> mpd->inode->i_blkbits);
- return err;
+ return;
}
BUG_ON(blks == 0);
@@ -2312,7 +2311,8 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
if (ext4_should_order_data(mpd->inode)) {
err = ext4_jbd2_file_inode(handle, mpd->inode);
if (err)
- return err;
+ /* This only happens if the journal is aborted */
+ return;
}
/*
@@ -2323,10 +2323,13 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
disksize = i_size_read(mpd->inode);
if (disksize > EXT4_I(mpd->inode)->i_disksize) {
ext4_update_i_disksize(mpd->inode, disksize);
- return ext4_mark_inode_dirty(handle, mpd->inode);
+ err = ext4_mark_inode_dirty(handle, mpd->inode);
+ /* XXX not sure what our error handling straegy is here */
}
- return 0;
+submit_io:
+ mpage_da_submit_io(mpd);
+ mpd->io_done = 1;
}
#define BH_FLAGS ((1 << BH_Uptodate) | (1 << BH_Mapped) | \
@@ -2403,9 +2406,7 @@ flush_it:
* We couldn't merge the block to our extent, so we
* need to flush current extent and start new one
*/
- if (mpage_da_map_blocks(mpd) == 0)
- mpage_da_submit_io(mpd);
- mpd->io_done = 1;
+ mpage_da_map_and_submit(mpd);
return;
}
@@ -2437,15 +2438,13 @@ static int __mpage_da_writepage(struct page *page,
if (mpd->next_page != page->index) {
/*
* Nope, we can't. So, we map non-allocated blocks
- * and start IO on them using writepage()
+ * and start IO on them
*/
if (mpd->next_page != mpd->first_page) {
- if (mpage_da_map_blocks(mpd) == 0)
- mpage_da_submit_io(mpd);
+ mpage_da_map_and_submit(mpd);
/*
* skip rest of the page in the page_vec
*/
- mpd->io_done = 1;
redirty_page_for_writepage(wbc, page);
unlock_page(page);
return MPAGE_DA_EXTENT_TAIL;
@@ -3071,9 +3070,7 @@ retry:
* them for I/O.
*/
if (!mpd.io_done && mpd.next_page != mpd.first_page) {
- if (mpage_da_map_blocks(&mpd) == 0)
- mpage_da_submit_io(&mpd);
- mpd.io_done = 1;
+ mpage_da_map_and_submit(&mpd);
ret = MPAGE_DA_EXTENT_TAIL;
}
trace_ext4_da_write_pages(inode, &mpd);
--
1.7.1
--
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