delay capable() check in ext4_has_free_blocks(

PATCH Superseded Eric Sandeen 2 participants 3 messages Oct 24, 2008 ext4 file system

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Eric Sandeen

author

2008-10-24 20:27 UTC #0 lore raw

PATCH 2/2 delay capable() check in ext4_has_free_blocks(

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]>

fs/ext4/balloc.c +15 ~~-12~~

Index: linux-2.6/fs/ext4/balloc.c
===================================================================
@@ -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,

Eric Sandeen

author

2008-10-24 20:41 UTC #1 lore raw

PATCH v2 2/2 delay capable() check in ext4_has_free_blocks(

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...)

fs/ext4/balloc.c +14 ~~-12~~

Index: linux-2.6/fs/ext4/balloc.c
===================================================================
@@ -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,

Mingming Cao

Reviewed-by on v1 2/2

2008-10-24 20:48 UTC #2 lore raw

In reply to Eric Sandeen

Quoted 8 lines · 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]>

Quoted 61 lines

Index: linux-2.6/fs/ext4/balloc.c
===================================================================

fs/ext4/balloc.c +15 ~~-13~~

@@ -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,
 
--

Quoted 3 lines

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