[PATCHv6 35/37] ext4: reserve larger jounral transaction for huge pages

Kirill A. Shutemov
2017-01-26T11:58:17Z

If huge pages enabled, in worst case with 2048 blocks underlying a page,
each possibly in a different block group we have much more metadata to
commit.

Let's update estimates accordingly.

I was not able to trigger bad situation without the patch as it's hard to
construct very fragmented filesystem, but hopefully this change would be
enough to address the concern.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
fs/ext4/ext4_jbd2.h | 16 +++++++++++++---
fs/ext4/inode.c | 34 +++++++++++++++++++++++++++-------
2 files changed, 40 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index f97611171023..6e4e534d6e98 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -353,11 +353,21 @@ static inline int ext4_journal_restart(handle_t *handle, int nblocks)
return 0;
}

+static inline int __ext4_journal_blocks_per_page(struct inode *inode, bool thp)
+{
+ int bpp = 0;
+ if (EXT4_JOURNAL(inode) != NULL) {
+ bpp = jbd2_journal_blocks_per_page(inode);
+ if (thp)
+ bpp <<= HPAGE_PMD_ORDER;
+ }
+ return bpp;
+}
+
static inline int ext4_journal_blocks_per_page(struct inode *inode)
{
- if (EXT4_JOURNAL(inode) != NULL)
- return jbd2_journal_blocks_per_page(inode);
- return 0;
+ return __ext4_journal_blocks_per_page(inode,
+ (inode->i_flags & S_HUGE_MODE) != S_HUGE_NEVER);
}

static inline int ext4_journal_force_commit(journal_t *journal)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 5bf68bbe65ec..c30562b6e685 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -141,6 +141,7 @@ static int __ext4_journalled_writepage(struct page *page, unsigned int len);
static int ext4_bh_delay_or_unwritten(handle_t *handle, struct buffer_head *bh);
static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
int pextents);
+static int __ext4_writepage_trans_blocks(struct inode *inode, int bpp);

/*
* Test whether an inode is a fast symlink.
@@ -4496,6 +4497,21 @@ void ext4_set_inode_flags(struct inode *inode)
!ext4_should_journal_data(inode) && !ext4_has_inline_data(inode) &&
!ext4_encrypted_inode(inode))
new_fl |= S_DAX;
+
+ if ((new_fl & S_HUGE_MODE) != S_HUGE_NEVER &&
+ EXT4_JOURNAL(inode) != NULL) {
+ int bpp = __ext4_journal_blocks_per_page(inode, true);
+ int credits = __ext4_writepage_trans_blocks(inode, bpp);
+
+ if (EXT4_JOURNAL(inode)->j_max_transaction_buffers < credits) {
+ pr_warn_once("EXT4-fs (%s): "
+ "journal is too small for huge pages. "
+ "Disable huge pages support.\n",
+ inode->i_sb->s_id);
+ new_fl &= ~S_HUGE_MODE;
+ }
+ }
+
inode_set_flags(inode, new_fl,
S_SYNC|S_APPEND|S_IMMUTABLE|S_NOATIME|S_DIRSYNC|S_DAX);
}
@@ -5471,6 +5487,16 @@ static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
return ret;
}

+static int __ext4_writepage_trans_blocks(struct inode *inode, int bpp)
+{
+ int ret = ext4_meta_trans_blocks(inode, bpp, bpp);
+
+ /* Account for data blocks for journalled mode */
+ if (ext4_should_journal_data(inode))
+ ret += bpp;
+ return ret;
+}
+
/*
* Calculate the total number of credits to reserve to fit
* the modification of a single pages into a single transaction,
@@ -5484,14 +5510,8 @@ static int ext4_meta_trans_blocks(struct inode *inode, int lblocks,
int ext4_writepage_trans_blocks(struct inode *inode)
{
int bpp = ext4_journal_blocks_per_page(inode);
- int ret;
-
- ret = ext4_meta_trans_blocks(inode, bpp, bpp);

- /* Account for data blocks for journalled mode */
- if (ext4_should_journal_data(inode))
- ret += bpp;
- return ret;
+ return __ext4_writepage_trans_blocks(inode, bpp);
}

/*