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NTFS: - Split ntfs_map_runlist() into ntfs_map_runlist() and a non-locking

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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>
This commit is contained in:
Anton Altaparmakov 2005-02-15 10:08:43 +00:00
parent 1a0df15acd
commit b6ad6c52fe
6 changed files with 119 additions and 113 deletions
Download patch file Download diff file Expand all files Collapse all files

107
fs/ntfs/attrib.c
View file

@ -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 @@ int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
}
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 @@ int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
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 @@ err_out:
}
/**
* 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 @@ err_out:
* 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 @@ lock_retry_remap:
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 @@ lock_retry_remap:
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);
}