NTFS: - Split ntfs_map_runlist() into ntfs_map_runlist() and a non-locking
helper ntfs_map_runlist_nolock() which is used by ntfs_map_runlist().
This allows us to map runlist fragments with the runlist lock already
held without having to drop and reacquire it around the call. Adapt
all callers.
- Change ntfs_find_vcn() to ntfs_find_vcn_nolock() which takes a locked
runlist. This allows us to find runlist elements with the runlist
lock already held without having to drop and reacquire it around the
call. Adapt all callers.
Signed-off-by: Anton Altaparmakov <aia21@cantab.net>
diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
index 7d66846..7a16f7c 100644
--- a/fs/ntfs/attrib.c
+++ b/fs/ntfs/attrib.c
@@ -1,7 +1,7 @@
/**
* attrib.c - NTFS attribute operations. Part of the Linux-NTFS project.
*
- * Copyright (c) 2001-2004 Anton Altaparmakov
+ * Copyright (c) 2001-2005 Anton Altaparmakov
* Copyright (c) 2002 Richard Russon
*
* This program/include file is free software; you can redistribute it and/or
@@ -30,7 +30,7 @@
#include "types.h"
/**
- * ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
+ * ntfs_map_runlist_nolock - map (a part of) a runlist of an ntfs inode
* @ni: ntfs inode for which to map (part of) a runlist
* @vcn: map runlist part containing this vcn
*
@@ -38,24 +38,23 @@
*
* Return 0 on success and -errno on error.
*
- * Locking: - The runlist must be unlocked on entry and is unlocked on return.
- * - This function takes the lock for writing and modifies the runlist.
+ * Locking: - The runlist must be locked for writing.
+ * - This function modifies the runlist.
*/
-int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
+int ntfs_map_runlist_nolock(ntfs_inode *ni, VCN vcn)
{
ntfs_inode *base_ni;
- ntfs_attr_search_ctx *ctx;
MFT_RECORD *mrec;
+ ntfs_attr_search_ctx *ctx;
+ runlist_element *rl;
int err = 0;
ntfs_debug("Mapping runlist part containing vcn 0x%llx.",
(unsigned long long)vcn);
-
if (!NInoAttr(ni))
base_ni = ni;
else
base_ni = ni->ext.base_ntfs_ino;
-
mrec = map_mft_record(base_ni);
if (IS_ERR(mrec))
return PTR_ERR(mrec);
@@ -66,15 +65,7 @@
}
err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
CASE_SENSITIVE, vcn, NULL, 0, ctx);
- if (unlikely(err))
- goto put_err_out;
-
- down_write(&ni->runlist.lock);
- /* Make sure someone else didn't do the work while we were sleeping. */
- if (likely(ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn) <=
- LCN_RL_NOT_MAPPED)) {
- runlist_element *rl;
-
+ if (likely(!err)) {
rl = ntfs_mapping_pairs_decompress(ni->vol, ctx->attr,
ni->runlist.rl);
if (IS_ERR(rl))
@@ -82,9 +73,6 @@
else
ni->runlist.rl = rl;
}
- up_write(&ni->runlist.lock);
-
-put_err_out:
ntfs_attr_put_search_ctx(ctx);
err_out:
unmap_mft_record(base_ni);
@@ -92,17 +80,45 @@
}
/**
- * ntfs_find_vcn - find a vcn in the runlist described by an ntfs inode
- * @ni: ntfs inode describing the runlist to search
- * @vcn: vcn to find
- * @need_write: if false, lock for reading and if true, lock for writing
+ * ntfs_map_runlist - map (a part of) a runlist of an ntfs inode
+ * @ni: ntfs inode for which to map (part of) a runlist
+ * @vcn: map runlist part containing this vcn
+ *
+ * Map the part of a runlist containing the @vcn of the ntfs inode @ni.
+ *
+ * Return 0 on success and -errno on error.
+ *
+ * Locking: - The runlist must be unlocked on entry and is unlocked on return.
+ * - This function takes the runlist lock for writing and modifies the
+ * runlist.
+ */
+int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
+{
+ int err = 0;
+
+ down_write(&ni->runlist.lock);
+ /* Make sure someone else didn't do the work while we were sleeping. */
+ if (likely(ntfs_rl_vcn_to_lcn(ni->runlist.rl, vcn) <=
+ LCN_RL_NOT_MAPPED))
+ err = ntfs_map_runlist_nolock(ni, vcn);
+ up_write(&ni->runlist.lock);
+ return err;
+}
+
+/**
+ * ntfs_find_vcn_nolock - find a vcn in the runlist described by an ntfs inode
+ * @ni: ntfs inode describing the runlist to search
+ * @vcn: vcn to find
+ * @write_locked: true if the runlist is locked for writing
*
* Find the virtual cluster number @vcn in the runlist described by the ntfs
* inode @ni and return the address of the runlist element containing the @vcn.
- * The runlist is left locked and the caller has to unlock it. If @need_write
- * is true, the runlist is locked for writing and if @need_write is false, the
- * runlist is locked for reading. In the error case, the runlist is not left
- * locked.
+ * The runlist is left locked and the caller has to unlock it. In the error
+ * case, the runlist is left in the same locking state as on entry.
+ *
+ * Note if @write_locked is FALSE the lock may be dropped inside the function
+ * so you cannot rely on the runlist still being the same when this function
+ * returns.
*
* Note you need to distinguish between the lcn of the returned runlist element
* being >= 0 and LCN_HOLE. In the later case you have to return zeroes on
@@ -124,28 +140,24 @@
* true, it is locked for writing. Otherwise is is locked for
* reading.
*/
-runlist_element *ntfs_find_vcn(ntfs_inode *ni, const VCN vcn,
- const BOOL need_write)
+runlist_element *ntfs_find_vcn_nolock(ntfs_inode *ni, const VCN vcn,
+ const BOOL write_locked)
{
runlist_element *rl;
int err = 0;
BOOL is_retry = FALSE;
- ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, lock for %sing.",
+ ntfs_debug("Entering for i_ino 0x%lx, vcn 0x%llx, %s_locked.",
ni->mft_no, (unsigned long long)vcn,
- !need_write ? "read" : "writ");
+ write_locked ? "write" : "read");
BUG_ON(!ni);
BUG_ON(!NInoNonResident(ni));
BUG_ON(vcn < 0);
-lock_retry_remap:
- if (!need_write)
- down_read(&ni->runlist.lock);
- else
- down_write(&ni->runlist.lock);
+retry_remap:
rl = ni->runlist.rl;
if (likely(rl && vcn >= rl[0].vcn)) {
while (likely(rl->length)) {
- if (likely(vcn < rl[1].vcn)) {
+ if (unlikely(vcn < rl[1].vcn)) {
if (likely(rl->lcn >= LCN_HOLE)) {
ntfs_debug("Done.");
return rl;
@@ -161,19 +173,23 @@
err = -EIO;
}
}
- if (!need_write)
- up_read(&ni->runlist.lock);
- else
- up_write(&ni->runlist.lock);
if (!err && !is_retry) {
/*
* The @vcn is in an unmapped region, map the runlist and
* retry.
*/
- err = ntfs_map_runlist(ni, vcn);
+ if (!write_locked) {
+ up_read(&ni->runlist.lock);
+ down_write(&ni->runlist.lock);
+ }
+ err = ntfs_map_runlist_nolock(ni, vcn);
+ if (!write_locked) {
+ up_write(&ni->runlist.lock);
+ down_read(&ni->runlist.lock);
+ }
if (likely(!err)) {
is_retry = TRUE;
- goto lock_retry_remap;
+ goto retry_remap;
}
/*
* -EINVAL and -ENOENT coming from a failed mapping attempt are
@@ -184,7 +200,8 @@
err = -EIO;
} else if (!err)
err = -EIO;
- ntfs_error(ni->vol->sb, "Failed with error code %i.", err);
+ if (err != -ENOENT)
+ ntfs_error(ni->vol->sb, "Failed with error code %i.", err);
return ERR_PTR(err);
}