On Mon, Feb 25, 2008 at 10:13:39AM -0500, Theodore Tso wrote:

On Sun, Feb 24, 2008 at 09:20:50PM -0700, Andreas Dilger wrote:

quoted

On Feb 22, 2008  19:15 -0500, Theodore Ts'o wrote:

quoted

So before the recent patch were we actually creating long symlinks in
extents format?  Or were we just setting the flag but still treating
them as a block number?  If it was the latter, I guess we can put in
code into e2fsck to detect that case, and convert it back to a
singleton block number.  

Eric informed me that the long symlinks were actually stored in extent
mapped blocks.  That is not harmful, because it can only be a single
block and it will always fit into the inode.  The other thing to note
is that extent mapping is REQUIRED for > 32-bit blocknumbers, so we
may as well fix e2fsprogs to allow these symlinks to be handled normally.

Well, at least some kernel versions (as of sometime just before
2.6.25, iirc) were storing the long symlink as a single block in
i_block[0], despite EXTENTS_FL being set.  Valerie noticed this, and I
confirmed it, as it caused the mainline e2fsck extents support to core
dump.  Basically, what this means is that e2fsprogs can't trust
EXTENTS_FL for long symlinks.

But you do raise a good point that we need to support using the
extents format in order to support blocks > 2**32, so we can't just
arbitrary convert all symlinks to the old-style direct block maps.

How about the patch like below on top of the patch queue. Patch queue
currently enable extent flag only for directory and file . This patch
add it to normal symlink. With this fast symlink still have the extent
format enabled. I guess this would need a patch to the interim branch of
e2fsprogs to allow normal symlink to have extent format.

-aneesh

ext4: Enable extent format for symlink.

From: Aneesh Kumar K.V <redacted>

This patch enable extent format for normal symlink. Extent format enables
to refere file system blocks > 32 bits. Enabling extent format for symlink
enables to have symlink block beyond 2**32 blocks. We still don't enable
extent format for fast symlink.

Signed-off-by: Aneesh Kumar K.V <redacted>
---

 fs/ext4/ialloc.c |    4 ++--
 fs/ext4/namei.c  |    2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 78d1094..1462189 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c

@@ -842,8 +842,8 @@ got:
 		goto fail_free_drop;
 	}
 	if (test_opt(sb, EXTENTS)) {
-		/* set extent flag only for diretory and file */
-		if (S_ISDIR(mode) || S_ISREG(mode)) {
+		/* set extent flag only for diretory, file and normal symlink*/
+		if (S_ISDIR(mode) || S_ISREG(mode) || S_ISLNK(mode)) {
 			EXT4_I(inode)->i_flags |= EXT4_EXTENTS_FL;
 			ext4_ext_tree_init(handle, inode);
 			err = ext4_update_incompat_feature(handle, sb,

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index da942bc..63c33e0 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c

@@ -2222,6 +2222,8 @@ retry:
 			goto out_stop;
 		}
 	} else {
+		/* clear the extent format for fast symlink */
+		EXT4_I(inode)->i_flags &= ~EXT4_EXTENTS_FL;
 		inode->i_op = &ext4_fast_symlink_inode_operations;
 		memcpy((char*)&EXT4_I(inode)->i_data,symname,l);
 		inode->i_size = l-1;