Re: [PATCH] Btrfs: fix btrfs_ordered_update_i_size to update disk_i_size properly

[Liu Bo]

On Thu, Dec 01, 2016 at 01:46:10PM -0800, Liu Bo wrote:
> btrfs_ordered_update_i_size can be called by truncate and endio, but only 
> endio
> takes ordered_extent which contains the completed IO.
> 
> while truncating down a file, if there are some in-flight IOs,
> btrfs_ordered_update_i_size in endio will set disk_i_size to @orig_offset that
> is zero.  If truncating-down fails somehow, we try to recover in memory isize
> with this zero'd disk_i_size.
> 
> Fix it by only updating disk_i_size with @orig_offset when
> btrfs_ordered_update_i_size is not called from endio while truncating down and
> waiting for in-flight IOs completing their work before recover in-memory size.
> 
> Besides fixing the above issue, add an assertion for last_size to double check
> we truncate down to the desired size.
> 
> Signed-off-by: Liu Bo 
> ---
>  fs/btrfs/inode.c| 14 ++
>  fs/btrfs/ordered-data.c |  9 +++--
>  2 files changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index 09157dd..ef3594d 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4682,6 +4682,13 @@ int btrfs_truncate_inode_items(struct 
> btrfs_trans_handle *trans,
>  
>   btrfs_free_path(path);
>  
> + if (err == 0) {
> + /* only inline file may have last_size != new_size */
> + if (new_size >= root->sectorsize ||
> + new_size > root->fs_info->max_inline)
> + ASSERT(last_size == new_size);
> + }
> +

This ASSERT has been hit by fstests/generic/299, and it didn't show up
the first time I tested, I'm trying to figure out whether we have
problems in code or in this ASSERT.

Thanks,

-liubo

>   if (be_nice && bytes_deleted > SZ_32M) {
>   unsigned long updates = trans->delayed_ref_updates;
>   if (updates) {
> @@ -5064,6 +5071,13 @@ static int btrfs_setsize(struct inode *inode, struct 
> iattr *attr)
>   if (ret && inode->i_nlink) {
>   int err;
>  
> + /* To get a stable disk_i_size */
> + err = btrfs_wait_ordered_range(inode, 0, (u64)-1);
> + if (err) {
> + btrfs_orphan_del(NULL, inode);
> + return err;
> + }
> +
>   /*
>* failed to truncate, disk_i_size is only adjusted down
>* as we remove extents, so it should represent the true
> diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
> index b2d1e95..5eaa25a 100644
> --- a/fs/btrfs/ordered-data.c
> +++ b/fs/btrfs/ordered-data.c
> @@ -982,8 +982,13 @@ int btrfs_ordered_update_i_size(struct inode *inode, u64 
> offset,
>   }
>   disk_i_size = BTRFS_I(inode)->disk_i_size;
>  
> - /* truncate file */
> - if (disk_i_size > i_size) {
> + /*
> +  * truncate file.
> +  * If ordered is not NULL, then this is called from endio and
> +  * disk_i_size will be updated by either truncate itself or any
> +  * in-flight IOs which are inside the disk_i_size.
> +  */
> + if (!ordered && disk_i_size > i_size) {
>   BTRFS_I(inode)->disk_i_size = orig_offset;
>   ret = 0;
>   goto out;
> -- 
> 2.5.5
> 
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[PATCH] Btrfs: fix btrfs_ordered_update_i_size to update disk_i_size properly

[Liu Bo]

btrfs_ordered_update_i_size can be called by truncate and endio, but only endio
takes ordered_extent which contains the completed IO.

while truncating down a file, if there are some in-flight IOs,
btrfs_ordered_update_i_size in endio will set disk_i_size to @orig_offset that
is zero.  If truncating-down fails somehow, we try to recover in memory isize
with this zero'd disk_i_size.

Fix it by only updating disk_i_size with @orig_offset when
btrfs_ordered_update_i_size is not called from endio while truncating down and
waiting for in-flight IOs completing their work before recover in-memory size.

Besides fixing the above issue, add an assertion for last_size to double check
we truncate down to the desired size.

Signed-off-by: Liu Bo 
---
 fs/btrfs/inode.c| 14 ++
 fs/btrfs/ordered-data.c |  9 +++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 09157dd..ef3594d 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4682,6 +4682,13 @@ int btrfs_truncate_inode_items(struct btrfs_trans_handle 
*trans,
 
btrfs_free_path(path);
 
+   if (err == 0) {
+   /* only inline file may have last_size != new_size */
+   if (new_size >= root->sectorsize ||
+   new_size > root->fs_info->max_inline)
+   ASSERT(last_size == new_size);
+   }
+
if (be_nice && bytes_deleted > SZ_32M) {
unsigned long updates = trans->delayed_ref_updates;
if (updates) {
@@ -5064,6 +5071,13 @@ static int btrfs_setsize(struct inode *inode, struct 
iattr *attr)
if (ret && inode->i_nlink) {
int err;
 
+   /* To get a stable disk_i_size */
+   err = btrfs_wait_ordered_range(inode, 0, (u64)-1);
+   if (err) {
+   btrfs_orphan_del(NULL, inode);
+   return err;
+   }
+
/*
 * failed to truncate, disk_i_size is only adjusted down
 * as we remove extents, so it should represent the true
diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index b2d1e95..5eaa25a 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -982,8 +982,13 @@ int btrfs_ordered_update_i_size(struct inode *inode, u64 
offset,
}
disk_i_size = BTRFS_I(inode)->disk_i_size;
 
-   /* truncate file */
-   if (disk_i_size > i_size) {
+   /*
+* truncate file.
+* If ordered is not NULL, then this is called from endio and
+* disk_i_size will be updated by either truncate itself or any
+* in-flight IOs which are inside the disk_i_size.
+*/
+   if (!ordered && disk_i_size > i_size) {
BTRFS_I(inode)->disk_i_size = orig_offset;
ret = 0;
goto out;
-- 
2.5.5

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