diff options
| author | Theodore Ts'o <tytso@mit.edu> | 2015-10-03 10:49:23 -0400 |
|---|---|---|
| committer | Mister Oyster <oysterized@gmail.com> | 2017-12-31 01:44:57 +0100 |
| commit | 0a1c35eaa245f0a901ee0b84f68826099db9bd97 (patch) | |
| tree | 572dca517191492f7a48206f435ce0e6aabf3e92 /fs/ext4 | |
| parent | f556a9fb4fbe2e4904fe4b10bef9e653690c18b0 (diff) | |
ext4: optimize ext4_writepage() for attempted 4k delalloc writes
In cases where the file system block size is the same as the page
size, and ext4_writepage() is asked to write out a page which is
either has the unwritten bit set in the extent tree, or which does not
yet have a block assigned due to delayed allocation, we can bail out
early and, unlocking the page earlier and avoiding a round trip
through ext4_bio_write_page() with the attendant calls to
set_page_writeback() and redirty_page_for_writeback().
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Joe Maples <joe@frap129.org>
Diffstat (limited to 'fs/ext4')
| -rw-r--r-- | fs/ext4/inode.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 61543a761..6c9f59415 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1845,11 +1845,22 @@ static int ext4_writepage(struct page *page, * the page. But we may reach here when we do a journal commit via * journal_submit_inode_data_buffers() and in that case we must write * allocated buffers to achieve data=ordered mode guarantees. + * + * Also, if there is only one buffer per page (the fs block + * size == the page size), if one buffer needs block + * allocation or needs to modify the extent tree to clear the + * unwritten flag, we know that the page can't be written at + * all, so we might as well refuse the write immediately. + * Unfortunately if the block size != page size, we can't as + * easily detect this case using ext4_walk_page_buffers(), but + * for the extremely common case, this is an optimization that + * skips a useless round trip through ext4_bio_write_page(). */ if (ext4_walk_page_buffers(NULL, page_bufs, 0, len, NULL, ext4_bh_delay_or_unwritten)) { redirty_page_for_writepage(wbc, page); - if (current->flags & PF_MEMALLOC) { + if ((current->flags & PF_MEMALLOC) || + (inode->i_sb->s_blocksize == PAGE_CACHE_SIZE)) { /* * For memory cleaning there's no point in writing only * some buffers. So just bail out. Warn if we came here |