[PATCH] ext4: Avoid excessive credit estimate in ext4_tmpfile()

[PATCH] ext4: Avoid excessive credit estimate in ext4_tmpfile()

[Jan Kara]

A user with minimum journal size (1024 blocks these days) complained
about the following error triggered by generic/697 test in
ext4_tmpfile():

run fstests generic/697 at 2024-02-28 05:34:46
JBD2: vfstest wants too many credits credits:260 rsv_credits:0 max:256
EXT4-fs error (device loop0) in __ext4_new_inode:1083: error 28

Indeed the credit estimate in ext4_tmpfile() is huge.
EXT4_MAXQUOTAS_INIT_BLOCKS() is 219, then 10 credits from ext4_tmpfile()
itself and then ext4_xattr_credits_for_new_inode() adds more credits
needed for security attributes and ACLs. Now the
EXT4_MAXQUOTAS_INIT_BLOCKS() is in fact unnecessary because we've
already initialized quotas with dquot_init() shortly before and so
EXT4_MAXQUOTAS_TRANS_BLOCKS() is enough (which boils down to 3 credits).

Fixes: af51a2ac36d1 ("ext4: ->tmpfile() support")
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/ext4/namei.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 05b647e6bc19..58fee3c6febc 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2898,7 +2898,7 @@ static int ext4_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
 	inode = ext4_new_inode_start_handle(idmap, dir, mode,
 					    NULL, 0, NULL,
 					    EXT4_HT_DIR,
-			EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
+			EXT4_MAXQUOTAS_TRANS_BLOCKS(dir->i_sb) +
 			  4 + EXT4_XATTR_TRANS_BLOCKS);
 	handle = ext4_journal_current_handle();
 	err = PTR_ERR(inode);
-- 
2.35.3

Re: [PATCH] ext4: Avoid excessive credit estimate in ext4_tmpfile()

[Luis Henriques]

Jan Kara <jack@suse.cz> writes:

> A user with minimum journal size (1024 blocks these days) complained
> about the following error triggered by generic/697 test in
> ext4_tmpfile():
>
> run fstests generic/697 at 2024-02-28 05:34:46
> JBD2: vfstest wants too many credits credits:260 rsv_credits:0 max:256
> EXT4-fs error (device loop0) in __ext4_new_inode:1083: error 28
>
> Indeed the credit estimate in ext4_tmpfile() is huge.
> EXT4_MAXQUOTAS_INIT_BLOCKS() is 219, then 10 credits from ext4_tmpfile()
> itself and then ext4_xattr_credits_for_new_inode() adds more credits
> needed for security attributes and ACLs. Now the
> EXT4_MAXQUOTAS_INIT_BLOCKS() is in fact unnecessary because we've
> already initialized quotas with dquot_init() shortly before and so
> EXT4_MAXQUOTAS_TRANS_BLOCKS() is enough (which boils down to 3 credits).
>
> Fixes: af51a2ac36d1 ("ext4: ->tmpfile() support")
> Signed-off-by: Jan Kara <jack@suse.cz>

FWIW, I've run generic/697 with a 1GiB device, with a block size of 65536.
Without this patch the test fails.  Feel free to add my

Tested-by: Luis Henriques <lhenriques@suse.de>

Cheers,
-- 
Luís

> ---
>  fs/ext4/namei.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 05b647e6bc19..58fee3c6febc 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2898,7 +2898,7 @@ static int ext4_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
>  	inode = ext4_new_inode_start_handle(idmap, dir, mode,
>  					    NULL, 0, NULL,
>  					    EXT4_HT_DIR,
> -			EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
> +			EXT4_MAXQUOTAS_TRANS_BLOCKS(dir->i_sb) +
>  			  4 + EXT4_XATTR_TRANS_BLOCKS);
>  	handle = ext4_journal_current_handle();
>  	err = PTR_ERR(inode);
> -- 
>
> 2.35.3
>

Re: [PATCH] ext4: Avoid excessive credit estimate in ext4_tmpfile()

[Disha Goel]

On 07/03/24 5:23 pm, Jan Kara wrote:

> A user with minimum journal size (1024 blocks these days) complained
> about the following error triggered by generic/697 test in
> ext4_tmpfile():
>
> run fstests generic/697 at 2024-02-28 05:34:46
> JBD2: vfstest wants too many credits credits:260 rsv_credits:0 max:256
> EXT4-fs error (device loop0) in __ext4_new_inode:1083: error 28
>
> Indeed the credit estimate in ext4_tmpfile() is huge.
> EXT4_MAXQUOTAS_INIT_BLOCKS() is 219, then 10 credits from ext4_tmpfile()
> itself and then ext4_xattr_credits_for_new_inode() adds more credits
> needed for security attributes and ACLs. Now the
> EXT4_MAXQUOTAS_INIT_BLOCKS() is in fact unnecessary because we've
> already initialized quotas with dquot_init() shortly before and so
> EXT4_MAXQUOTAS_TRANS_BLOCKS() is enough (which boils down to 3 credits).
>
> Fixes: af51a2ac36d1 ("ext4: ->tmpfile() support")
> Signed-off-by: Jan Kara <jack@suse.cz>

Thanks for the fix patch. I have tested the patch on a power machine with smaller
disk and journal size, generic/697 test passed (for both bs<ps and bs=ps) and no
longer seeing the error.

Feel free to add:
Tested-by: Disha Goel<disgoel@linux.ibm.com>

> ---
>   fs/ext4/namei.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 05b647e6bc19..58fee3c6febc 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -2898,7 +2898,7 @@ static int ext4_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
>   	inode = ext4_new_inode_start_handle(idmap, dir, mode,
>   					    NULL, 0, NULL,
>   					    EXT4_HT_DIR,
> -			EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
> +			EXT4_MAXQUOTAS_TRANS_BLOCKS(dir->i_sb) +
>   			  4 + EXT4_XATTR_TRANS_BLOCKS);
>   	handle = ext4_journal_current_handle();
>   	err = PTR_ERR(inode);

Re: [PATCH] ext4: Avoid excessive credit estimate in ext4_tmpfile()

[Theodore Ts'o]

On Thu, 07 Mar 2024 12:53:20 +0100, Jan Kara wrote:
> A user with minimum journal size (1024 blocks these days) complained
> about the following error triggered by generic/697 test in
> ext4_tmpfile():
> 
> run fstests generic/697 at 2024-02-28 05:34:46
> JBD2: vfstest wants too many credits credits:260 rsv_credits:0 max:256
> EXT4-fs error (device loop0) in __ext4_new_inode:1083: error 28
> 
> [...]

Applied, thanks!

[1/1] ext4: Avoid excessive credit estimate in ext4_tmpfile()
      commit: 35a1f12f0ca857fee1d7a04ef52cbd5f1f84de13

Best regards,
-- 
Theodore Ts'o <tytso@mit.edu>