在 2008-08-19二的 12:18 +0530，Aneesh Kumar K.V写道：
> We need to make sure adding new buffer_head to the
> contiguous block extent doesn't result in nrblocks
> greater than EXT4_MAX_TRANS_DATA. We only have
> enought credit to insert EXT4_MAX_TRANS_DATA blocks.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Mingming Cao <cmm@xxxxxxxxxx>
> ---
> fs/ext4/inode.c | 38 +++++++++++++++++++++++++-------------
> 1 files changed, 25 insertions(+), 13 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index dcd1337..a10f8e5 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1909,27 +1909,39 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
> static void mpage_add_bh_to_extent(struct mpage_da_data *mpd,
> sector_t logical, struct buffer_head *bh)
> {
> - struct buffer_head *lbh = &mpd->lbh;
> sector_t next;
> + size_t b_size = bh->b_size;
> + struct buffer_head *lbh = &mpd->lbh;
> int nrblocks = lbh->b_size >> mpd->inode->i_blkbits;
>
> /* check if thereserved journal credits might overflow */
> - if (!(EXT4_I(mpd->inode)->i_flags & EXT4_EXTENTS_FL) &&
> - (nrblocks >= EXT4_MAX_TRANS_DATA))
> - /*
> - * With noextent format we are limited by the journal
> - * credit available. Total credit needed to insert
> - * nrblocks contiguous blocks is dependent on the
> - * nrblocks. So limit nrblocks.
> - */
> - goto flush_it;
> -
> + if (!(EXT4_I(mpd->inode)->i_flags & EXT4_EXTENTS_FL)) {
> + if (nrblocks >= EXT4_MAX_TRANS_DATA) {
> + /*
> + * With noextent format we are limited by the journal
> + * credit available. Total credit needed to insert
> + * nrblocks contiguous blocks is dependent on the
> + * nrblocks. So limit nrblocks.
> + */
> + goto flush_it;
> + } else if ((nrblocks + (b_size >> mpd->inode->i_blkbits)) >
> + EXT4_MAX_TRANS_DATA) {
> + /*
> + * Adding the new buffer_head would make it cross the
> + * allowed limit for which we have journal credit
> + * reserved. So limit the new bh->b_size
> + */
> + b_size = (EXT4_MAX_TRANS_DATA - nrblocks) <<
> + mpd->inode->i_blkbits;
> + /* we will do mpage_da_submit_io in the next loop */
> + }
> + }
> /*
> * First block in the extent
> */
> if (lbh->b_size == 0) {
> lbh->b_blocknr = logical;
> - lbh->b_size = bh->b_size;
> + lbh->b_size = b_size;
> lbh->b_state = bh->b_state & BH_FLAGS;
> return;
> }
> @@ -1939,7 +1951,7 @@ static void mpage_add_bh_to_extent(struct mpage_da_data *mpd,
> * Can we merge the block to our big extent?
> */
> if (logical == next && (bh->b_state & BH_FLAGS) == lbh->b_state) {
> - lbh->b_size += bh->b_size;
> + lbh->b_size += b_size;
> return;
> }
>
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