[PATCH] btrfs/extent_io.c: return -ENOMEM instead of BUG_ON on allocation failure in set_extent_bit if __GFP_WAIT is set in the mask

[PATCH] btrfs/extent_io.c: return -ENOMEM instead of BUG_ON on allocation failure in set_extent_bit if __GFP_WAIT is set in the mask

[Wang Sheng-Hui]

If __GFP_WAIT is set in the mask, set_extent_bit should return
-ENOMEM to its caller to decide what to do on allocation failure,
instead of BUG_ON.

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
---
 fs/btrfs/extent_io.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index b67814c..fd2411e 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -720,7 +720,8 @@ int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
 again:
 	if (!prealloc && (mask & __GFP_WAIT)) {
 		prealloc = alloc_extent_state(mask);
-		BUG_ON(!prealloc);
+		if (!prealloc)
+			return -ENOMEM;
 	}
 
 	spin_lock(&tree->lock);
-- 
1.7.1

Re: [PATCH] btrfs/extent_io.c: return -ENOMEM instead of BUG_ON on allocation failure in set_extent_bit if __GFP_WAIT is set in the mask

[Jeff Mahoney]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 03/31/2012 03:25 AM, Wang Sheng-Hui wrote:
> If __GFP_WAIT is set in the mask, set_extent_bit should return 
> -ENOMEM to its caller to decide what to do on allocation failure, 
> instead of BUG_ON.
> 
> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com> --- 
> fs/btrfs/extent_io.c |    3 ++- 1 files changed, 2 insertions(+), 1
> deletions(-)
> 
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index
> b67814c..fd2411e 100644 --- a/fs/btrfs/extent_io.c +++
> b/fs/btrfs/extent_io.c @@ -720,7 +720,8 @@ int
> set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end, 
> again: if (!prealloc && (mask & __GFP_WAIT)) { prealloc =
> alloc_extent_state(mask); -		BUG_ON(!prealloc); +		if (!prealloc) +
> return -ENOMEM; }
> 
> spin_lock(&tree->lock);

Hi Sheng-Hui -

Do you have a follow-on series to this? With the exception of the
set_extent_dirty call in end_bio_extent_readpage, every set_extent_bit
caller uses GFP_NOFS, which includes __GFP_WAIT. If we return a
failure here, we need to catch the failure in the call sites.
Otherwise, the failure will just be ignored and we'll end up with an
inconsistent extent state tree.

- -Jeff

- -- 
Jeff Mahoney
SUSE Labs
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.18 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
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=Pxwh
-----END PGP SIGNATURE-----

Re: [PATCH] btrfs/extent_io.c: return -ENOMEM instead of BUG_ON on allocation failure in set_extent_bit if __GFP_WAIT is set in the mask

[Wang Sheng-Hui]

On 2012=E5=B9=B404=E6=9C=8804=E6=97=A5 21:29, Jeff Mahoney wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>=20
> On 03/31/2012 03:25 AM, Wang Sheng-Hui wrote:
>> If __GFP_WAIT is set in the mask, set_extent_bit should return=20
>> -ENOMEM to its caller to decide what to do on allocation failure,=20
>> instead of BUG_ON.
>>
>> Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com> ---=20
>> fs/btrfs/extent_io.c |    3 ++- 1 files changed, 2 insertions(+), 1
>> deletions(-)
>>
>> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index
>> b67814c..fd2411e 100644 --- a/fs/btrfs/extent_io.c +++
>> b/fs/btrfs/extent_io.c @@ -720,7 +720,8 @@ int
>> set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,=20
>> again: if (!prealloc && (mask & __GFP_WAIT)) { prealloc =3D
>> alloc_extent_state(mask); -		BUG_ON(!prealloc); +		if (!prealloc) +
>> return -ENOMEM; }
>>
>> spin_lock(&tree->lock);
>=20
> Hi Sheng-Hui -
>=20
> Do you have a follow-on series to this? With the exception of the
> set_extent_dirty call in end_bio_extent_readpage, every set_extent_bi=
t
> caller uses GFP_NOFS, which includes __GFP_WAIT. If we return a
> failure here, we need to catch the failure in the call sites.
> Otherwise, the failure will just be ignored and we'll end up with an
> inconsistent extent state tree.
>=20
> - -Jeff
>=20

Hi Jeff,

I'll review the code and provide a list of patches later.
Currently we can skip it, I think.

Thanks,
Sheng-Hui

> - --=20
> Jeff Mahoney
> SUSE Labs
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v2.0.18 (GNU/Linux)
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
>=20
> iQIcBAEBAgAGBQJPfEzIAAoJEB57S2MheeWyqcoP/RagYePToMYOdgjjxVz2cwkf
> BLT5B0KWWaJa0KtEOpgQATmldmA4CCq6WmC7R/Omy1q9RD75rheKxaxuQY35NTFe
> czBSfVr3VeMy1A6dIK+wHOiAfheuT90xSgXJJMpdkjHmNjEA1g2nupAFltUE/L70
> +xFxotBuoYuTe8u++QES0JGqnw8YI6FW0z3Z4buyoqRhgiX7TukNfXXgx4c2HI0/
> cOkxyvYpDi2WF9EtESn/ekwf4Rjx9kNUX/9owmDWYgHD4MLjwSQsRbwZ7BrZEM3k
> aBe8yZGpgr3UuL9nGiPbWHsyBeAskvXaL6Y2YIczJSvsoP/DM+9SsHAwnqkVaBHv
> 8qQiQqUhF1mrdl3GBSvKJarGczrSmbWZ5X94oYq4MCKyi3SeTN/bcJS+p5EV1Tvs
> LMRqqj26leHnl+bYKGWIfJqQRuYcfbkzTOADbn54iMYj2aG2raUjI9D53TUIInuV
> Csm2hhKJn+HDwu2+gZX1F99W0ehs1ps86oGfkT4WA/H7fTmugiEYxsM1Dk71Ti7/
> eadns62DYFZyzKk4/jP/8Rjygc4YM/T2F9qb+SX3hWGhIIZiz5qOxjgBZy91i+84
> W+DDUHjZPU+O14nNlKFA3INGS9823ENklRkzpNUhLx7ffrCLOAS73O2rzHcaSmtk
> FSDWO4EqxIAi4t3LoL14
> =3DPxwh
> -----END PGP SIGNATURE-----