Re: ENOSPC returned during writepages

Mingming Cao
2008-08-21T18:06:19Z

在 2008-08-21四的 23:01 +0530，Aneesh Kumar K.V写道：
> On Thu, Aug 21, 2008 at 10:07:37AM -0700, Mingming Cao wrote:
> >
> > 在 2008-08-21四的 22:15 +0530，Aneesh Kumar K.V写道：
> > > On Wed, Aug 20, 2008 at 11:13:39AM +0530, Aneesh Kumar K.V wrote:
> > > > Hi,
> > > >
> > > > I am getting this even with the latest patch queue. The test program is
> > > > a modified fsstress with fallocate support.
> > > >
> > > > mpage_da_map_blocks block allocation failed for inode 377954 at logical
> > > > offset 313 with max blocks 4 with error -28
> > > > mpage_da_map_blocks block allocation failed for inode 336367 at logical
> > > > offset 74 with max blocks 9 with error -28
> > > > mpage_da_map_blocks block allocation failed for inode 345560 at logical
> > > > offset 542 with max blocks 7 with error -28
> > > > This should not happen.!! Data will be lost
> > > > mpage_da_map_blocks block allocation failed for inode 355317 at logical
> > > > offset 152 with max blocks 10 with error -28
> > > > This should not happen.!! Data will be lost
> > > > mpage_da_map_blocks block allocation failed for inode 395261 at logical
> > > > offset 462 with max blocks 1 with error -28
> > > > This should not happen.!! Data will be lost
> > > > mpage_da_map_blocks block allocation failed for inode 323784 at logical
> > > > offset 313 with max blocks 11 with error -28
> > > > This should not happen.!! Data will be lost
> > > >
> > >
> > > With this patch i am not seeing error. It does the below
> > >
> > > a) use ext4_claim_free_blocks that also update the free blocks count
> > > b) Later after block allocation update the free blocks count if we
> > > allocated less with non-delayed mode
> > > c) Switch to non delay mode if we are low on free blocks.
> > >
> > I had sent a patch to do c) yesterday, I noticed that we can't switch to
> > non delayed mode if the inode already have some delalloc dirty pages.
> >
> >
> > > @@ -2462,11 +2464,21 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
> > > unsigned from, to;
> > > struct inode *inode = mapping->host;
> > > handle_t *handle;
> > > + s64 free_blocks;
> > > + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
> > >
> > > index = pos >> PAGE_CACHE_SHIFT;
> > > from = pos & (PAGE_CACHE_SIZE - 1);
> > > to = from + len;
> > >
> > > + free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
> > > + if (free_blocks < (4 * (FBC_BATCH * nr_cpu_ids))) {
> > > + /* switch to non delalloc mode */
> > > + *fsdata = (void *)1;
> > > + return ext4_write_begin(file, mapping, pos,
> > > + len, flags, pagep, fsdata);
> > > + }
> > > + *fsdata = (void *)0;
> >
> > No, calling ext4_write_begin() directly won't work, as it start a
> > handle, do the block allocation , and leave the handle there. It
> > expect later the write_end aops to file the inode to the transaction
> > list, and close that handle.
> >
> > With your change, the aops write_end still points to the
> > ext4_da_write_end(), which doesn't match the ext4_write_begin. We need
> > to switch the aop write_begin/write_end function pointers all together.
> >
>
> My patch does it in a simple way. I am attaching only switch to non
> delalloc patch below. It is still being tested.
>

For the people on the mailing list, after chatted with Aneesh on IRC I
realize how it is handle it now:) He passed a special flag to
da_write_end() to indicating fall back to normal write_end() in the case
the ext4_da_write_begin() falls back to normal write_begin. It's not
very obvious so I missed it in the first place.

Mingming
> commit 490b69bd47b9ea27b1bb86bbdfb85a2911047149
> Author: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> Date: Thu Aug 21 22:10:50 2008 +0530
>
> switch to non-delalloc
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index d965a05..087abca 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -1030,11 +1030,17 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
> BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
> mdb_free = EXT4_I(inode)->i_reserved_meta_blocks - mdb;
>
> - /* Account for allocated meta_blocks */
> - mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
> + if (mdb_free) {
> + /* Account for allocated meta_blocks */
> + mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
>
> - /* update fs free blocks counter for truncate case */
> - percpu_counter_add(&sbi->s_freeblocks_counter, mdb_free);
> + /*
> + * We have reserved more blocks.
> + * Now free the extra blocks reserved
> + */
> + percpu_counter_add(&sbi->s_freeblocks_counter, mdb_free);
> + EXT4_I(inode)->i_allocated_meta_blocks = 0;
> + }
>
> /* update per-inode reservations */
> BUG_ON(used > EXT4_I(inode)->i_reserved_data_blocks);
> @@ -1042,7 +1048,6 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
>
> BUG_ON(mdb > EXT4_I(inode)->i_reserved_meta_blocks);
> EXT4_I(inode)->i_reserved_meta_blocks = mdb;
> - EXT4_I(inode)->i_allocated_meta_blocks = 0;
> spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
> }
>
> @@ -2459,11 +2464,21 @@ static int ext4_da_write_begin(struct file *file, struct address_space *mapping,
> unsigned from, to;
> struct inode *inode = mapping->host;
> handle_t *handle;
> + s64 free_blocks;
> + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
>
> index = pos >> PAGE_CACHE_SHIFT;
> from = pos & (PAGE_CACHE_SIZE - 1);
> to = from + len;
>
> + free_blocks = percpu_counter_read_positive(&sbi->s_freeblocks_counter);
> + if (free_blocks < (4 * (FBC_BATCH * nr_cpu_ids))) {
> + /* switch to non delalloc mode */
> + *fsdata = (void *)1;
> + return ext4_write_begin(file, mapping, pos,
> + len, flags, pagep, fsdata);
> + }
> + *fsdata = (void *)0;
> retry:
> /*
> * With delayed allocation, we don't log the i_disksize update
> @@ -2532,6 +2547,19 @@ static int ext4_da_write_end(struct file *file,
> handle_t *handle = ext4_journal_current_handle();
> loff_t new_i_size;
> unsigned long start, end;
> + int low_free_blocks = (int)fsdata;
> +
> + if (low_free_blocks) {
> + if (ext4_should_order_data(inode)) {
> + return ext4_ordered_write_end(file, mapping, pos,
> + len, copied, page, fsdata);
> + } else if (ext4_should_writeback_data(inode)) {
> + return ext4_writeback_write_end(file, mapping, pos,
> + len, copied, page, fsdata);
> + } else {
> + BUG();
> + }
> + }
>
> start = pos & (PAGE_CACHE_SIZE - 1);
> end = start + copied -1;
> --
> To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html