Hi, Filipe Manana > -----Original Message----- > From: Filipe Manana [mailto:fdmanana@xxxxxxxxx] > Sent: Thursday, January 21, 2016 4:49 AM > To: Zhao Lei <zhaolei@xxxxxxxxxxxxxx> > Cc: linux-btrfs@xxxxxxxxxxxxxxx > Subject: Re: [PATCH 1/3] btrfs: Continue write in case of can_not_nocow > > On Wed, Jan 6, 2016 at 11:00 AM, Zhao Lei <zhaolei@xxxxxxxxxxxxxx> wrote: > > btrfs failed in xfstests btrfs/080 with -o nodatacow. > > > > Can be reproduced by following script: > > DEV=/dev/vdg > > MNT=/mnt/tmp > > > > umount $DEV &>/dev/null > > mkfs.btrfs -f $DEV > > mount -o nodatacow $DEV $MNT > > > > dd if=/dev/zero of=$MNT/test bs=1 count=2048 & > > btrfs subvolume snapshot -r $MNT $MNT/test_snap & > > wait > > -- > > We can see dd failed on NO_SPACE. > > > > Reason: > > __btrfs_buffered_write should run cow write when no_cow impossible, > > and current code is designed with above logic. > > But check_can_nocow() have 2 type of return value(0 and <0) on > > can_not_no_cow, and current code only continue write on first case, > > the second case happened in doing subvolume. > > > > Fix: > > Continue write when check_can_nocow() return 0 and <0. > > > > Signed-off-by: Zhao Lei <zhaolei@xxxxxxxxxxxxxx> > Reviewed-by: Filipe Manana <fdmanana@xxxxxxxx> > Thanks for review. > Could you please submit a test case for xfstests as well? btrfs/080 with -o nodatacow already can trigger this bug. Thanks Zhaolei > Thanks. > > > --- > > fs/btrfs/file.c | 37 +++++++++++++++++-------------------- > > 1 file changed, 17 insertions(+), 20 deletions(-) > > > > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 977e715..11fd981 > > 100644 > > --- a/fs/btrfs/file.c > > +++ b/fs/btrfs/file.c > > @@ -1516,27 +1516,24 @@ static noinline ssize_t > > __btrfs_buffered_write(struct file *file, > > > > reserve_bytes = num_pages << PAGE_CACHE_SHIFT; > > > > - if (BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW | > > - > BTRFS_INODE_PREALLOC)) { > > - ret = check_can_nocow(inode, pos, > &write_bytes); > > - if (ret < 0) > > - break; > > - if (ret > 0) { > > - /* > > - * For nodata cow case, no need to > reserve > > - * data space. > > - */ > > - only_release_metadata = true; > > - /* > > - * our prealloc extent may be smaller > than > > - * write_bytes, so scale down. > > - */ > > - num_pages = > DIV_ROUND_UP(write_bytes + offset, > > - > PAGE_CACHE_SIZE); > > - reserve_bytes = num_pages << > PAGE_CACHE_SHIFT; > > - goto reserve_metadata; > > - } > > + if ((BTRFS_I(inode)->flags & (BTRFS_INODE_NODATACOW > | > > + > BTRFS_INODE_PREALLOC)) && > > + check_can_nocow(inode, pos, &write_bytes) > 0) { > > + /* > > + * For nodata cow case, no need to reserve > > + * data space. > > + */ > > + only_release_metadata = true; > > + /* > > + * our prealloc extent may be smaller than > > + * write_bytes, so scale down. > > + */ > > + num_pages = DIV_ROUND_UP(write_bytes + > offset, > > + > PAGE_CACHE_SIZE); > > + reserve_bytes = num_pages << > PAGE_CACHE_SHIFT; > > + goto reserve_metadata; > > } > > + > > ret = btrfs_check_data_free_space(inode, pos, > write_bytes); > > if (ret < 0) > > break; > > -- > > 1.8.5.1 > > > > > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" > > in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo > > info at http://vger.kernel.org/majordomo-info.html > > > > -- > Filipe David Manana, > > "Reasonable men adapt themselves to the world. > Unreasonable men adapt the world to themselves. > That's why all progress depends on unreasonable men." -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
