* 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
+ * @ctx: active attribute search context if present or NULL if not
*
* Map the part of a runlist containing the @vcn of the ntfs inode @ni.
*
+ * If @ctx is specified, it is an active search context of @ni and its base mft
+ * record. This is needed when ntfs_map_runlist_nolock() encounters unmapped
+ * runlist fragments and allows their mapping. If you do not have the mft
+ * record mapped, you can specify @ctx as NULL and ntfs_map_runlist_nolock()
+ * will perform the necessary mapping and unmapping.
+ *
+ * Note, ntfs_map_runlist_nolock() saves the state of @ctx on entry and
+ * restores it before returning. Thus, @ctx will be left pointing to the same
+ * attribute on return as on entry. However, the actual pointers in @ctx may
+ * point to different memory locations on return, so you must remember to reset
+ * any cached pointers from the @ctx, i.e. after the call to
+ * ntfs_map_runlist_nolock(), you will probably want to do:
+ * m = ctx->mrec;
+ * a = ctx->attr;
+ * Assuming you cache ctx->attr in a variable @a of type ATTR_RECORD * and that
+ * you cache ctx->mrec in a variable @m of type MFT_RECORD *.
+ *
* Return 0 on success and -errno on error. There is one special error code
* which is not an error as such. This is -ENOENT. It means that @vcn is out
* of bounds of the runlist.
* Note the runlist can be NULL after this function returns if @vcn is zero and
* the attribute has zero allocated size, i.e. there simply is no runlist.
*
- * Locking: - The runlist must be locked for writing.
- * - This function modifies the runlist.
+ * WARNING: If @ctx is supplied, regardless of whether success or failure is
+ * returned, you need to check IS_ERR(@ctx->mrec) and if TRUE the @ctx
+ * is no longer valid, i.e. you need to either call
+ * ntfs_attr_reinit_search_ctx() or ntfs_attr_put_search_ctx() on it.
+ * In that case PTR_ERR(@ctx->mrec) will give you the error code for
+ * why the mapping of the old inode failed.
+ *
+ * Locking: - The runlist described by @ni must be locked for writing on entry
+ * and is locked on return. Note the runlist will be modified.
+ * - If @ctx is NULL, the base mft record of @ni must not be mapped on
+ * entry and it will be left unmapped on return.
+ * - If @ctx is not NULL, the base mft record must be mapped on entry
+ * and it will be left mapped on return.
*/
-int ntfs_map_runlist_nolock(ntfs_inode *ni, VCN vcn)
+int ntfs_map_runlist_nolock(ntfs_inode *ni, VCN vcn, ntfs_attr_search_ctx *ctx)
{
VCN end_vcn;
+ unsigned long flags;
ntfs_inode *base_ni;
MFT_RECORD *m;
ATTR_RECORD *a;
- ntfs_attr_search_ctx *ctx;
runlist_element *rl;
- unsigned long flags;
+ struct page *put_this_page = NULL;
int err = 0;
+ BOOL ctx_is_temporary, ctx_needs_reset;
+ ntfs_attr_search_ctx old_ctx;
ntfs_debug("Mapping runlist part containing vcn 0x%llx.",
(unsigned long long)vcn);
base_ni = ni;
else
base_ni = ni->ext.base_ntfs_ino;
- m = map_mft_record(base_ni);
- if (IS_ERR(m))
- return PTR_ERR(m);
- ctx = ntfs_attr_get_search_ctx(base_ni, m);
- if (unlikely(!ctx)) {
- err = -ENOMEM;
- goto err_out;
+ if (!ctx) {
+ ctx_is_temporary = ctx_needs_reset = TRUE;
+ m = map_mft_record(base_ni);
+ if (IS_ERR(m))
+ return PTR_ERR(m);
+ ctx = ntfs_attr_get_search_ctx(base_ni, m);
+ if (unlikely(!ctx)) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ } else {
+ VCN allocated_size_vcn;
+
+ BUG_ON(IS_ERR(ctx->mrec));
+ a = ctx->attr;
+ BUG_ON(!a->non_resident);
+ ctx_is_temporary = FALSE;
+ end_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn);
+ read_lock_irqsave(&ni->size_lock, flags);
+ allocated_size_vcn = ni->allocated_size >>
+ ni->vol->cluster_size_bits;
+ read_unlock_irqrestore(&ni->size_lock, flags);
+ if (!a->data.non_resident.lowest_vcn && end_vcn <= 0)
+ end_vcn = allocated_size_vcn - 1;
+ /*
+ * If we already have the attribute extent containing @vcn in
+ * @ctx, no need to look it up again. We slightly cheat in
+ * that if vcn exceeds the allocated size, we will refuse to
+ * map the runlist below, so there is definitely no need to get
+ * the right attribute extent.
+ */
+ if (vcn >= allocated_size_vcn || (a->type == ni->type &&
+ a->name_length == ni->name_len &&
+ !memcmp((u8*)a + le16_to_cpu(a->name_offset),
+ ni->name, ni->name_len) &&
+ sle64_to_cpu(a->data.non_resident.lowest_vcn)
+ <= vcn && end_vcn >= vcn))
+ ctx_needs_reset = FALSE;
+ else {
+ /* Save the old search context. */
+ old_ctx = *ctx;
+ /*
+ * If the currently mapped (extent) inode is not the
+ * base inode we will unmap it when we reinitialize the
+ * search context which means we need to get a
+ * reference to the page containing the mapped mft
+ * record so we do not accidentally drop changes to the
+ * mft record when it has not been marked dirty yet.
+ */
+ if (old_ctx.base_ntfs_ino && old_ctx.ntfs_ino !=
+ old_ctx.base_ntfs_ino) {
+ put_this_page = old_ctx.ntfs_ino->page;
+ page_cache_get(put_this_page);
+ }
+ /*
+ * Reinitialize the search context so we can lookup the
+ * needed attribute extent.
+ */
+ ntfs_attr_reinit_search_ctx(ctx);
+ ctx_needs_reset = TRUE;
+ }
}
- err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
- CASE_SENSITIVE, vcn, NULL, 0, ctx);
- if (unlikely(err)) {
- if (err == -ENOENT)
- err = -EIO;
- goto err_out;
+ if (ctx_needs_reset) {
+ err = ntfs_attr_lookup(ni->type, ni->name, ni->name_len,
+ CASE_SENSITIVE, vcn, NULL, 0, ctx);
+ if (unlikely(err)) {
+ if (err == -ENOENT)
+ err = -EIO;
+ goto err_out;
+ }
+ BUG_ON(!ctx->attr->non_resident);
}
a = ctx->attr;
/*
* ntfs_mapping_pairs_decompress() fails.
*/
end_vcn = sle64_to_cpu(a->data.non_resident.highest_vcn) + 1;
- if (unlikely(!a->data.non_resident.lowest_vcn && end_vcn <= 1)) {
- read_lock_irqsave(&ni->size_lock, flags);
- end_vcn = ni->allocated_size >> ni->vol->cluster_size_bits;
- read_unlock_irqrestore(&ni->size_lock, flags);
- }
+ if (!a->data.non_resident.lowest_vcn && end_vcn == 1)
+ end_vcn = sle64_to_cpu(a->data.non_resident.allocated_size) >>
+ ni->vol->cluster_size_bits;
if (unlikely(vcn >= end_vcn)) {
err = -ENOENT;
goto err_out;
else
ni->runlist.rl = rl;
err_out:
- if (likely(ctx))
- ntfs_attr_put_search_ctx(ctx);
- unmap_mft_record(base_ni);
+ if (ctx_is_temporary) {
+ if (likely(ctx))
+ ntfs_attr_put_search_ctx(ctx);
+ unmap_mft_record(base_ni);
+ } else if (ctx_needs_reset) {
+ /*
+ * If there is no attribute list, restoring the search context
+ * is acomplished simply by copying the saved context back over
+ * the caller supplied context. If there is an attribute list,
+ * things are more complicated as we need to deal with mapping
+ * of mft records and resulting potential changes in pointers.
+ */
+ if (NInoAttrList(base_ni)) {
+ /*
+ * If the currently mapped (extent) inode is not the
+ * one we had before, we need to unmap it and map the
+ * old one.
+ */
+ if (ctx->ntfs_ino != old_ctx.ntfs_ino) {
+ /*
+ * If the currently mapped inode is not the
+ * base inode, unmap it.
+ */
+ if (ctx->base_ntfs_ino && ctx->ntfs_ino !=
+ ctx->base_ntfs_ino) {
+ unmap_extent_mft_record(ctx->ntfs_ino);
+ ctx->mrec = ctx->base_mrec;
+ BUG_ON(!ctx->mrec);
+ }
+ /*
+ * If the old mapped inode is not the base
+ * inode, map it.
+ */
+ if (old_ctx.base_ntfs_ino &&
+ old_ctx.ntfs_ino !=
+ old_ctx.base_ntfs_ino) {
+retry_map:
+ ctx->mrec = map_mft_record(
+ old_ctx.ntfs_ino);
+ /*
+ * Something bad has happened. If out
+ * of memory retry till it succeeds.
+ * Any other errors are fatal and we
+ * return the error code in ctx->mrec.
+ * Let the caller deal with it... We
+ * just need to fudge things so the
+ * caller can reinit and/or put the
+ * search context safely.
+ */
+ if (IS_ERR(ctx->mrec)) {
+ if (PTR_ERR(ctx->mrec) ==
+ -ENOMEM) {
+ schedule();
+ goto retry_map;
+ } else
+ old_ctx.ntfs_ino =
+ old_ctx.
+ base_ntfs_ino;
+ }
+ }
+ }
+ /* Update the changed pointers in the saved context. */
+ if (ctx->mrec != old_ctx.mrec) {
+ if (!IS_ERR(ctx->mrec))
+ old_ctx.attr = (ATTR_RECORD*)(
+ (u8*)ctx->mrec +
+ ((u8*)old_ctx.attr -
+ (u8*)old_ctx.mrec));
+ old_ctx.mrec = ctx->mrec;
+ }
+ }
+ /* Restore the search context to the saved one. */
+ *ctx = old_ctx;
+ /*
+ * We drop the reference on the page we took earlier. In the
+ * case that IS_ERR(ctx->mrec) is true this means we might lose
+ * some changes to the mft record that had been made between
+ * the last time it was marked dirty/written out and now. This
+ * at this stage is not a problem as the mapping error is fatal
+ * enough that the mft record cannot be written out anyway and
+ * the caller is very likely to shutdown the whole inode
+ * immediately and mark the volume dirty for chkdsk to pick up
+ * the pieces anyway.
+ */
+ if (put_this_page)
+ page_cache_release(put_this_page);
+ }
return err;
}
* of bounds of the runlist.
*
* 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.
+ * - This function takes the runlist lock for writing and may modify
+ * the runlist.
*/
int ntfs_map_runlist(ntfs_inode *ni, VCN vcn)
{
/* 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);
+ err = ntfs_map_runlist_nolock(ni, vcn, NULL);
up_write(&ni->runlist.lock);
return err;
}
goto retry_remap;
}
}
- err = ntfs_map_runlist_nolock(ni, vcn);
+ err = ntfs_map_runlist_nolock(ni, vcn, NULL);
if (!write_locked) {
up_write(&ni->runlist.lock);
down_read(&ni->runlist.lock);
goto retry_remap;
}
}
- err = ntfs_map_runlist_nolock(ni, vcn);
+ err = ntfs_map_runlist_nolock(ni, vcn, NULL);
if (!write_locked) {
up_write(&ni->runlist.lock);
down_read(&ni->runlist.lock);
projects / karo-tx-linux.git / commitdiff