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Date: Mon, 9 May 2011 19:41:35 +0300
From: amir73il@...rs.sourceforge.net
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu, Amir Goldstein <amir73il@...rs.sf.net>,
Yongqiang Yang <xiaoqiangnk@...il.com>
Subject: [PATCH RFC 17/30] ext4: snapshot control
From: Amir Goldstein <amir73il@...rs.sf.net>
Snapshot control with chsnap/lssnap.
Take/delete snapshot with chsnap +/-S.
Enable/disable snapshot with chsnap +/-n.
Show snapshot status with lssnap.
Signed-off-by: Amir Goldstein <amir73il@...rs.sf.net>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@...il.com>
---
fs/ext4/ext4.h | 2 +
fs/ext4/ioctl.c | 117 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 119 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 942cd9c..3cf6602 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -597,6 +597,8 @@ struct ext4_new_group_data {
/* note ioctl 10 reserved for an early version of the FIEMAP ioctl */
/* note ioctl 11 reserved for filesystem-independent FIEMAP ioctl */
#define EXT4_IOC_ALLOC_DA_BLKS _IO('f', 12)
+#define EXT4_IOC_GETSNAPFLAGS _IOR('f', 13, long)
+#define EXT4_IOC_SETSNAPFLAGS _IOW('f', 14, long)
#define EXT4_IOC_MOVE_EXT _IOWR('f', 15, struct move_extent)
#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index a426332..e100c04 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -83,6 +83,21 @@ long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
if (!capable(CAP_SYS_RESOURCE))
goto flags_out;
}
+
+ /*
+ * The SNAPFILE flag can only be changed on directories by
+ * the relevant capability.
+ * It can only be inherited by regular files.
+ */
+ if ((flags ^ oldflags) & EXT4_SNAPFILE_FL) {
+ if (!S_ISDIR(inode->i_mode)) {
+ err = -ENOTDIR;
+ goto flags_out;
+ }
+ if (!capable(CAP_SYS_RESOURCE))
+ goto flags_out;
+ }
+
if (oldflags & EXT4_EXTENTS_FL) {
/* We don't support clearning extent flags */
if (!(flags & EXT4_EXTENTS_FL)) {
@@ -139,6 +154,102 @@ flags_out:
mnt_drop_write(filp->f_path.mnt);
return err;
}
+ case EXT4_IOC_GETSNAPFLAGS:
+ if (!EXT4_SNAPSHOTS(inode->i_sb))
+ return -EOPNOTSUPP;
+
+ ext4_snapshot_get_flags(inode, filp);
+ flags = ext4_get_snapstate_flags(inode);
+ return put_user(flags, (int __user *) arg);
+
+ case EXT4_IOC_SETSNAPFLAGS: {
+ handle_t *handle = NULL;
+ struct ext4_iloc iloc;
+ unsigned int oldflags;
+ int err;
+
+ if (!EXT4_SNAPSHOTS(inode->i_sb))
+ return -EOPNOTSUPP;
+
+ if (!is_owner_or_cap(inode))
+ return -EACCES;
+
+ if (get_user(flags, (int __user *) arg))
+ return -EFAULT;
+
+ err = mnt_want_write(filp->f_path.mnt);
+ if (err)
+ return err;
+
+ /*
+ * Snapshot file state flags can only be changed by
+ * the relevant capability and under snapshot_mutex lock.
+ */
+ if (!ext4_snapshot_file(inode) ||
+ !capable(CAP_SYS_RESOURCE))
+ return -EPERM;
+
+ /* update snapshot 'open' flag under i_mutex */
+ mutex_lock(&inode->i_mutex);
+ ext4_snapshot_get_flags(inode, filp);
+ oldflags = ext4_get_snapstate_flags(inode);
+
+ /*
+ * snapshot_mutex should be held throughout the trio
+ * snapshot_{set_flags,take,update}(). It must be taken
+ * before starting the transaction, otherwise
+ * journal_lock_updates() inside snapshot_take()
+ * can deadlock:
+ * A: journal_start()
+ * A: snapshot_mutex_lock()
+ * B: journal_start()
+ * B: snapshot_mutex_lock() (waiting for A)
+ * A: journal_stop()
+ * A: snapshot_take() ->
+ * A: journal_lock_updates() (waiting for B)
+ */
+ mutex_lock(&EXT4_SB(inode->i_sb)->s_snapshot_mutex);
+
+ handle = ext4_journal_start(inode, 1);
+ if (IS_ERR(handle)) {
+ err = PTR_ERR(handle);
+ goto snapflags_out;
+ }
+ err = ext4_reserve_inode_write(handle, inode, &iloc);
+ if (err)
+ goto snapflags_err;
+
+ err = ext4_snapshot_set_flags(handle, inode, flags);
+ if (err)
+ goto snapflags_err;
+
+ err = ext4_mark_iloc_dirty(handle, inode, &iloc);
+snapflags_err:
+ ext4_journal_stop(handle);
+ if (err)
+ goto snapflags_out;
+
+ if (!(oldflags & 1UL<<EXT4_SNAPSTATE_LIST) &&
+ (flags & 1UL<<EXT4_SNAPSTATE_LIST))
+ /* setting list flag - take snapshot */
+ err = ext4_snapshot_take(inode);
+snapflags_out:
+ if ((oldflags|flags) & 1UL<<EXT4_SNAPSTATE_LIST) {
+ /* if clearing list flag, cleanup snapshot list */
+ int ret;
+
+ /* update/cleanup snapshots list even if take failed */
+ ret = ext4_snapshot_update(inode->i_sb,
+ !(flags & 1UL<<EXT4_SNAPSTATE_LIST), 0);
+ if (!err)
+ err = ret;
+ }
+
+ mutex_unlock(&EXT4_SB(inode->i_sb)->s_snapshot_mutex);
+ mutex_unlock(&inode->i_mutex);
+ mnt_drop_write(filp->f_path.mnt);
+ return err;
+ }
case EXT4_IOC_GETVERSION:
case EXT4_IOC_GETVERSION_OLD:
return put_user(inode->i_generation, (int __user *) arg);
@@ -210,6 +321,8 @@ setversion_out:
if (get_user(n_blocks_count, (__u32 __user *)arg))
return -EFAULT;
+ /* avoid snapshot_take() in the middle of group_extend() */
+ mutex_lock(&EXT4_SB(sb)->s_snapshot_mutex);
err = mnt_want_write(filp->f_path.mnt);
if (err)
@@ -223,6 +336,7 @@ setversion_out:
}
if (err == 0)
err = err2;
+ mutex_unlock(&EXT4_SB(sb)->s_snapshot_mutex);
mnt_drop_write(filp->f_path.mnt);
return err;
@@ -285,6 +399,8 @@ mext_out:
if (err)
return err;
+ /* avoid snapshot_take() in the middle of group_add() */
+ mutex_lock(&EXT4_SB(sb)->s_snapshot_mutex);
err = ext4_group_add(sb, &input);
if (EXT4_SB(sb)->s_journal) {
jbd2_journal_lock_updates(EXT4_SB(sb)->s_journal);
@@ -293,6 +409,7 @@ mext_out:
}
if (err == 0)
err = err2;
+ mutex_unlock(&EXT4_SB(sb)->s_snapshot_mutex);
mnt_drop_write(filp->f_path.mnt);
return err;
--
1.7.0.4
--
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