Re: [PATCHv3 4/6] ext4: Make ext4_ind_map_blocks work with fiemap

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On 2/26/20 6:09 PM, Jan Kara wrote:
On Wed 26-02-20 15:27:06, Ritesh Harjani wrote:
For indirect block mapping if the i_block > max supported block in inode
then ext4_ind_map_blocks may return a -EIO error. But in case of fiemap
this could be a valid query to ext4_map_blocks.
So in case if !create then return 0. This also makes ext4_warning to
ext4_debug in ext4_block_to_path() for the same reason.

Signed-off-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>

Hmm, won't it be cleaner to just handle this in ext4_iomap_begin_report()?
We do trim map.m_len there anyway so it is only logical to trim it to
proper value supported by the inode on-disk format... BTW, note we have
sbi->s_bitmap_maxbytes value already computed in the superblock...

hmm. Yes, thanks for the pointers. Let me check this again.

-ritesh



								Honza

---
  fs/ext4/indirect.c | 11 +++++++++--
  1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index 3a4ab70fe9e0..e1ab495dd900 100644
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -102,7 +102,11 @@ static int ext4_block_to_path(struct inode *inode,
  		offsets[n++] = i_block & (ptrs - 1);
  		final = ptrs;
  	} else {
-		ext4_warning(inode->i_sb, "block %lu > max in inode %lu",
+		/*
+		 * It's not yet an error to just query beyond max
+		 * block in inode. Fiemap callers may do so.
+		 */
+		ext4_debug("block %lu > max in inode %lu",
  			     i_block + direct_blocks +
  			     indirect_blocks + double_blocks, inode->i_ino);
  	}
@@ -537,8 +541,11 @@ int ext4_ind_map_blocks(handle_t *handle, struct inode *inode,
  	depth = ext4_block_to_path(inode, map->m_lblk, offsets,
  				   &blocks_to_boundary);
- if (depth == 0)
+	if (depth == 0) {
+		if (!(flags & EXT4_GET_BLOCKS_CREATE))
+			err = 0;
  		goto out;
+	}
partial = ext4_get_branch(inode, depth, offsets, chain, &err); --
2.21.0





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