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| author | Theodore Ts'o <tytso@mit.edu> | 2015-10-03 16:49:23 +0200 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2015-10-03 16:49:23 +0200 |
| commit | cccd147a57e47527ce9c27fcd5f0a1c5669d6870 (patch) | |
| tree | 1cb956df150d20b0d1cf3f34fbf970b6a84561c5 /fs/ext4 | |
| parent | ext4 crypto: fix memory leak in ext4_bio_write_page() (diff) | |
| download | linux-cccd147a57e47527ce9c27fcd5f0a1c5669d6870.tar.xz linux-cccd147a57e47527ce9c27fcd5f0a1c5669d6870.zip | |
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>
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 612fbcf76b5c..c95d40658979 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -1815,11 +1815,22 @@ 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 |