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Date: Mon, 2 Feb 2015 18:05:10 +0100
From: Alexander Holler <holler@...oftware.de>
To: linux-fsdevel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Alexander Holler <holler@...oftware.de>
Subject: [PATCH 2/5] WIP: fs: fat: support unlinkat_s() for secure deletion of files
Signed-off-by: Alexander Holler <holler@...oftware.de>
---
fs/fat/fat.h | 1 +
fs/fat/fatent.c | 20 ++++++++++++++++++++
fs/fat/inode.c | 13 +++++++++++++
3 files changed, 34 insertions(+)
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index e0c4ba3..b9febda 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -81,6 +81,7 @@ struct msdos_sb_info {
unsigned int prev_free; /* previously allocated cluster number */
unsigned int free_clusters; /* -1 if undefined */
unsigned int free_clus_valid; /* is free_clusters valid? */
+ atomic_t secure_delete; /* delete blocks securely? */
struct fat_mount_options options;
struct nls_table *nls_disk; /* Codepage used on disk */
struct nls_table *nls_io; /* Charset used for input and display */
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 260705c..b3b9c11 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -575,6 +575,10 @@ int fat_free_clusters(struct inode *inode, int cluster)
goto error;
}
+ // TODO:
+ // if (atomic_read(&sbi->secure_delete) && secure_trim_available)
+ // use secure trim
+ // else
if (sbi->options.discard) {
/*
* Issue discard for the sectors we no longer
@@ -591,6 +595,22 @@ int fat_free_clusters(struct inode *inode, int cluster)
first_cl = cluster;
}
+ } else if (atomic_read(&sbi->secure_delete)) {
+ /*
+ * Fill blocks with zero for the sectors we no
+ * longer care about, batching contiguous clusters
+ * into one request.
+ */
+ if (cluster != fatent.entry + 1) {
+ int nr_clus = fatent.entry - first_cl + 1;
+
+ sb_issue_zeroout(sb,
+ fat_clus_to_blknr(sbi, first_cl),
+ nr_clus * sbi->sec_per_clus,
+ GFP_NOFS);
+
+ first_cl = cluster;
+ }
}
ops->ent_put(&fatent, FAT_ENT_FREE);
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 756aead..9073690 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -816,6 +816,17 @@ int fat_sync_inode(struct inode *inode)
EXPORT_SYMBOL_GPL(fat_sync_inode);
+static void fat_set_secure_delete(struct super_block *sb, bool secure)
+{
+ struct msdos_sb_info *sbi = MSDOS_SB(sb);
+ // TODO: will overflow with a very large number of
+ // concurrent calls of unlinkat_s().
+ if (secure)
+ atomic_inc(&sbi->secure_delete);
+ else
+ atomic_dec(&sbi->secure_delete);
+}
+
static int fat_show_options(struct seq_file *m, struct dentry *root);
static const struct super_operations fat_sops = {
.alloc_inode = fat_alloc_inode,
@@ -827,6 +838,7 @@ static const struct super_operations fat_sops = {
.remount_fs = fat_remount,
.show_options = fat_show_options,
+ .set_secure_delete = fat_set_secure_delete,
};
static int fat_show_options(struct seq_file *m, struct dentry *root)
@@ -1580,6 +1592,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat,
sbi->root_cluster = 0;
sbi->free_clusters = -1; /* Don't know yet */
sbi->free_clus_valid = 0;
+ atomic_set(&sbi->secure_delete, 0);
sbi->prev_free = FAT_START_ENT;
sb->s_maxbytes = 0xffffffff;
--
2.1.0
--
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