ext4: add ext4_sb_bread() to disambiguate ENOMEM cases

Today, when sb_bread() returns NULL, this can either be because of an
I/O error or because the system failed to allocate the buffer.  Since
it's an old interface, changing would require changing many call
sites.

So instead we create our own ext4_sb_bread(), which also allows us to
set the REQ_META flag.

Also fixed a problem in the xattr code where a NULL return in a
function could also mean that the xattr was not found, which could
lead to the wrong error getting returned to userspace.

Fixes: ac27a0ec112a ("ext4: initial copy of files from ext3")
Cc: stable@kernel.org # 2.6.19
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 36 insertions, 40 deletions

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 7643d52c776c..510c9bb7ce71 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -522,14 +522,13 @@ ext4_xattr_block_get(struct inode *inode, int name_index, const char *name,
 	ea_idebug(inode, "name=%d.%s, buffer=%p, buffer_size=%ld",
 		  name_index, name, buffer, (long)buffer_size);
 
-	error = -ENODATA;
 	if (!EXT4_I(inode)->i_file_acl)
-		goto cleanup;
+		return -ENODATA;
 	ea_idebug(inode, "reading block %llu",
 		  (unsigned long long)EXT4_I(inode)->i_file_acl);
-	bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
-	if (!bh)
-		goto cleanup;
+	bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+	if (IS_ERR(bh))
+		return PTR_ERR(bh);
 	ea_bdebug(bh, "b_count=%d, refcount=%d",
 		atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
 	error = ext4_xattr_check_block(inode, bh);
@@ -696,26 +695,23 @@ ext4_xattr_block_list(struct dentry *dentry, char *buffer, size_t buffer_size)
 	ea_idebug(inode, "buffer=%p, buffer_size=%ld",
 		  buffer, (long)buffer_size);
 
-	error = 0;
 	if (!EXT4_I(inode)->i_file_acl)
-		goto cleanup;
+		return 0;
 	ea_idebug(inode, "reading block %llu",
 		  (unsigned long long)EXT4_I(inode)->i_file_acl);
-	bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
-	error = -EIO;
-	if (!bh)
-		goto cleanup;
+	bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+	if (IS_ERR(bh))
+		return PTR_ERR(bh);
 	ea_bdebug(bh, "b_count=%d, refcount=%d",
 		atomic_read(&(bh->b_count)), le32_to_cpu(BHDR(bh)->h_refcount));
 	error = ext4_xattr_check_block(inode, bh);
 	if (error)
 		goto cleanup;
 	ext4_xattr_block_cache_insert(EA_BLOCK_CACHE(inode), bh);
-	error = ext4_xattr_list_entries(dentry, BFIRST(bh), buffer, buffer_size);
-
+	error = ext4_xattr_list_entries(dentry, BFIRST(bh), buffer,
+					buffer_size);
 cleanup:
 	brelse(bh);
-
 	return error;
 }
 
@@ -830,9 +826,9 @@ int ext4_get_inode_usage(struct inode *inode, qsize_t *usage)
 	}
 
 	if (EXT4_I(inode)->i_file_acl) {
-		bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
-		if (!bh) {
-			ret = -EIO;
+		bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+		if (IS_ERR(bh)) {
+			ret = PTR_ERR(bh);
 			goto out;
 		}
 
@@ -1821,16 +1817,15 @@ ext4_xattr_block_find(struct inode *inode, struct ext4_xattr_info *i,
 
 	if (EXT4_I(inode)->i_file_acl) {
 		/* The inode already has an extended attribute block. */
-		bs->bh = sb_bread(sb, EXT4_I(inode)->i_file_acl);
-		error = -EIO;
-		if (!bs->bh)
-			goto cleanup;
+		bs->bh = ext4_sb_bread(sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+		if (IS_ERR(bs->bh))
+			return PTR_ERR(bs->bh);
 		ea_bdebug(bs->bh, "b_count=%d, refcount=%d",
 			atomic_read(&(bs->bh->b_count)),
 			le32_to_cpu(BHDR(bs->bh)->h_refcount));
 		error = ext4_xattr_check_block(inode, bs->bh);
 		if (error)
-			goto cleanup;
+			return error;
 		/* Find the named attribute. */
 		bs->s.base = BHDR(bs->bh);
 		bs->s.first = BFIRST(bs->bh);
@@ -1839,13 +1834,10 @@ ext4_xattr_block_find(struct inode *inode, struct ext4_xattr_info *i,
 		error = xattr_find_entry(inode, &bs->s.here, bs->s.end,
 					 i->name_index, i->name, 1);
 		if (error && error != -ENODATA)
-			goto cleanup;
+			return error;
 		bs->s.not_found = error;
 	}
-	error = 0;
-
-cleanup:
-	return error;
+	return 0;
 }
 
 static int
@@ -2274,9 +2266,9 @@ static struct buffer_head *ext4_xattr_get_block(struct inode *inode)
 
 	if (!EXT4_I(inode)->i_file_acl)
 		return NULL;
-	bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
-	if (!bh)
-		return ERR_PTR(-EIO);
+	bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+	if (IS_ERR(bh))
+		return bh;
 	error = ext4_xattr_check_block(inode, bh);
 	if (error) {
 		brelse(bh);
@@ -2746,10 +2738,11 @@ retry:
 	if (EXT4_I(inode)->i_file_acl) {
 		struct buffer_head *bh;
 
-		bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
-		error = -EIO;
-		if (!bh)
+		bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+		if (IS_ERR(bh)) {
+			error = PTR_ERR(bh);
 			goto cleanup;
+		}
 		error = ext4_xattr_check_block(inode, bh);
 		if (error) {
 			brelse(bh);
@@ -2903,11 +2896,12 @@ int ext4_xattr_delete_inode(handle_t *handle, struct inode *inode,
 	}
 
 	if (EXT4_I(inode)->i_file_acl) {
-		bh = sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl);
-		if (!bh) {
-			EXT4_ERROR_INODE(inode, "block %llu read error",
-					 EXT4_I(inode)->i_file_acl);
-			error = -EIO;
+		bh = ext4_sb_bread(inode->i_sb, EXT4_I(inode)->i_file_acl, REQ_PRIO);
+		if (IS_ERR(bh)) {
+			error = PTR_ERR(bh);
+			if (error == -EIO)
+				EXT4_ERROR_INODE(inode, "block %llu read error",
+						 EXT4_I(inode)->i_file_acl);
 			goto cleanup;
 		}
 		error = ext4_xattr_check_block(inode, bh);
@@ -3060,8 +3054,10 @@ ext4_xattr_block_cache_find(struct inode *inode,
 	while (ce) {
 		struct buffer_head *bh;
 
-		bh = sb_bread(inode->i_sb, ce->e_value);
-		if (!bh) {
+		bh = ext4_sb_bread(inode->i_sb, ce->e_value, REQ_PRIO);
+		if (IS_ERR(bh)) {
+			if (PTR_ERR(bh) == -ENOMEM)
+				return NULL;
 			EXT4_ERROR_INODE(inode, "block %lu read error",
 					 (unsigned long)ce->e_value);
 		} else if (ext4_xattr_cmp(header, BHDR(bh)) == 0) {