On 11/26/2011 11:13 PM, Yongqiang Yang wrote: > Hi, > > It can be tested by xfstests 61 or 91, I did not remember which one. ok, I will try it later. But I still wonder how it happens. See my comments below. > > It can be reproduced by reading on a fallocted block and write the block > after the fallocted block. Then the written block can not be written > out by da_writepages. Why? in read no bh will be created, and in write only the written bh will be mapped and set unwritten. How could that happen? Sorry, but this explanation doesn't convince me. > > Yongqiang. > > On Saturday, November 26, 2011, Tao Ma <tm@xxxxxx <mailto:tm@xxxxxx>> wrote: >> Hi Yongqiang, >> On 11/23/2011 05:15 PM, Yongqiang Yang wrote: >>> If there is a unwritten but clean buffer in a page and there is a > dirty buffer >>> after the buffer, then mpage_submit_io does not write the dirty > buffer out. >>> As a result, da_writepages loops forever. >> Did you ever meet with this bug or just find it to be a possible bug by >> skimming the code? Actually, I can't find a proper way to get a buffer >> which can satisfy the check. >> >> Thanks >> Tao >>> >>> This patch fixes the problem by checking dirty flag. >>> >>> Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx > <mailto:xiaoqiangnk@xxxxxxxxx>> >>> --- >>> fs/ext4/inode.c | 7 +++++-- >>> 1 files changed, 5 insertions(+), 2 deletions(-) >>> >>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c >>> index 755f6c7..20a1d17 100644 >>> --- a/fs/ext4/inode.c >>> +++ b/fs/ext4/inode.c >>> @@ -1339,8 +1339,11 @@ static int mpage_da_submit_io(struct > mpage_da_data *mpd, >>> clear_buffer_unwritten(bh); >>> } >>> >>> - /* skip page if block allocation undone */ >>> - if (buffer_delay(bh) || > buffer_unwritten(bh)) >>> + /* >>> + * skip page if block allocation undone and >>> + * block is dirty >>> + */ >>> + if (ext4_bh_delay_or_unwritten(NULL, bh)) >>> skip_page = 1; >>> bh = bh->b_this_page; >>> block_start += bh->b_size; >> >> >> > > -- > Best Wishes > Yongqiang Yang > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
