As reported by Eric Paris, the capable() check in ext4_has_free_blocks()
sometimes causes SELinux denials.
We can rearrange the logic so that we only try to use the root-reserved
blocks when necessary, and even then we can move the capable() test
to last, to avoid the check most of the time.
Signed-off-by: Eric Sandeen <[email protected]>
--
Index: linux-2.6/fs/ext4/balloc.c
===================================================================
--- linux-2.6.orig/fs/ext4/balloc.c 2008-10-24 14:43:11.103063953 -0500
+++ linux-2.6/fs/ext4/balloc.c 2008-10-24 14:43:18.082063765 -0500
@@ -596,23 +596,19 @@ void ext4_free_blocks(handle_t *handle,
*
* Check if filesystem has free blocks available for allocation.
* Return the number of blocks avaible for allocation for this request
- * On success, return nblocks
+ * On success, return 1, on failure, return 0.
*/
int ext4_has_free_blocks(struct ext4_sb_info *sbi,
s64 nblocks)
{
- s64 free_blocks, dirty_blocks;
- s64 root_blocks = 0;
+ s64 free_blocks, dirty_blocks, root_blocks;
struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
free_blocks = percpu_counter_read_positive(fbc);
dirty_blocks = percpu_counter_read_positive(dbc);
+ root_blocks = ext4_r_blocks_count(sbi->s_es);
- if (!capable(CAP_SYS_RESOURCE) &&
- sbi->s_resuid != current->fsuid &&
- (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
- root_blocks = ext4_r_blocks_count(sbi->s_es);
if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
EXT4_FREEBLOCKS_WATERMARK) {
@@ -625,13 +621,20 @@ int ext4_has_free_blocks(struct ext4_sb_
}
}
/* Check whether we have space after
- * accounting for current dirty blocks
+ * accounting for current dirty blocks & root reserved blocks.
*/
- if (free_blocks < ((root_blocks + nblocks) + dirty_blocks))
- /* we don't have free space */
- return 0;
+ if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
+ return 1;
- return 1;
+ /* Hm, nope. Are (enough) root reserved blocks available? */
+ if (sbi->s_resuid == current->fsuid ||
+ ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
+ capable(CAP_SYS_RESOURCE)) {
+ if (free_blocks >= (nblocks + dirty_blocks))
+ return 1;
+ }
+
+ return 0;
}
int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
As reported by Eric Paris, the capable() check in ext4_has_free_blocks()
sometimes causes SELinux denials.
We can rearrange the logic so that we only try to use the root-reserved
blocks when necessary, and even then we can move the capable() test
to last, to avoid the check most of the time.
Signed-off-by: Eric Sandeen <[email protected]>
---
(whoops, forgot a quilt refresh before sending the last one...)
Index: linux-2.6/fs/ext4/balloc.c
===================================================================
--- linux-2.6.orig/fs/ext4/balloc.c 2008-10-24 15:32:36.000000000 -0500
+++ linux-2.6/fs/ext4/balloc.c 2008-10-24 15:38:52.897001441 -0500
@@ -599,18 +599,13 @@ void ext4_free_blocks(handle_t *handle,
*/
int ext4_has_free_blocks(struct ext4_sb_info *sbi, s64 nblocks)
{
- s64 free_blocks, dirty_blocks;
- s64 root_blocks = 0;
+ s64 free_blocks, dirty_blocks, root_blocks;
struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
free_blocks = percpu_counter_read_positive(fbc);
dirty_blocks = percpu_counter_read_positive(dbc);
-
- if (!capable(CAP_SYS_RESOURCE) &&
- sbi->s_resuid != current->fsuid &&
- (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
- root_blocks = ext4_r_blocks_count(sbi->s_es);
+ root_blocks = ext4_r_blocks_count(sbi->s_es);
if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
EXT4_FREEBLOCKS_WATERMARK) {
@@ -623,13 +618,20 @@ int ext4_has_free_blocks(struct ext4_sb_
}
}
/* Check whether we have space after
- * accounting for current dirty blocks
+ * accounting for current dirty blocks & root reserved blocks.
*/
- if (free_blocks < ((root_blocks + nblocks) + dirty_blocks))
- /* we don't have free space */
- return 0;
+ if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
+ return 1;
- return 1;
+ /* Hm, nope. Are (enough) root reserved blocks available? */
+ if (sbi->s_resuid == current->fsuid ||
+ ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
+ capable(CAP_SYS_RESOURCE)) {
+ if (free_blocks >= (nblocks + dirty_blocks))
+ return 1;
+ }
+
+ return 0;
}
int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
在 2008-10-24五的 15:27 -0500，Eric Sandeen写道：
> As reported by Eric Paris, the capable() check in ext4_has_free_blocks()
> sometimes causes SELinux denials.
>
> We can rearrange the logic so that we only try to use the root-reserved
> blocks when necessary, and even then we can move the capable() test
> to last, to avoid the check most of the time.
>
> Signed-off-by: Eric Sandeen <[email protected]>
Reviewed-by: Mingming Cao <[email protected]>
> --
>
> Index: linux-2.6/fs/ext4/balloc.c
> ===================================================================
> --- linux-2.6.orig/fs/ext4/balloc.c 2008-10-24 14:43:11.103063953 -0500
> +++ linux-2.6/fs/ext4/balloc.c 2008-10-24 14:43:18.082063765 -0500
> @@ -596,23 +596,19 @@ void ext4_free_blocks(handle_t *handle,
> *
> * Check if filesystem has free blocks available for allocation.
> * Return the number of blocks avaible for allocation for this request
> - * On success, return nblocks
> + * On success, return 1, on failure, return 0.
> */
> int ext4_has_free_blocks(struct ext4_sb_info *sbi,
> s64 nblocks)
> {
> - s64 free_blocks, dirty_blocks;
> - s64 root_blocks = 0;
> + s64 free_blocks, dirty_blocks, root_blocks;
> struct percpu_counter *fbc = &sbi->s_freeblocks_counter;
> struct percpu_counter *dbc = &sbi->s_dirtyblocks_counter;
>
> free_blocks = percpu_counter_read_positive(fbc);
> dirty_blocks = percpu_counter_read_positive(dbc);
> + root_blocks = ext4_r_blocks_count(sbi->s_es);
>
> - if (!capable(CAP_SYS_RESOURCE) &&
> - sbi->s_resuid != current->fsuid &&
> - (sbi->s_resgid == 0 || !in_group_p(sbi->s_resgid)))
> - root_blocks = ext4_r_blocks_count(sbi->s_es);
>
> if (free_blocks - (nblocks + root_blocks + dirty_blocks) <
> EXT4_FREEBLOCKS_WATERMARK) {
> @@ -625,13 +621,20 @@ int ext4_has_free_blocks(struct ext4_sb_
> }
> }
> /* Check whether we have space after
> - * accounting for current dirty blocks
> + * accounting for current dirty blocks & root reserved blocks.
> */
> - if (free_blocks < ((root_blocks + nblocks) + dirty_blocks))
> - /* we don't have free space */
> - return 0;
> + if (free_blocks >= ((root_blocks + nblocks) + dirty_blocks))
> + return 1;
>
> - return 1;
> + /* Hm, nope. Are (enough) root reserved blocks available? */
> + if (sbi->s_resuid == current->fsuid ||
> + ((sbi->s_resgid != 0) && in_group_p(sbi->s_resgid)) ||
> + capable(CAP_SYS_RESOURCE)) {
> + if (free_blocks >= (nblocks + dirty_blocks))
> + return 1;
> + }
> +
> + return 0;
> }
>
> int ext4_claim_free_blocks(struct ext4_sb_info *sbi,
>
> --
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