diff options
Diffstat (limited to 'fs/ntfs/runlist.c')
| -rw-r--r-- | fs/ntfs/runlist.c | 132 |
1 files changed, 68 insertions, 64 deletions
diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c index f5b2ac929081..e2665d011d72 100644 --- a/fs/ntfs/runlist.c +++ b/fs/ntfs/runlist.c @@ -2,7 +2,7 @@ * runlist.c - NTFS runlist handling code. Part of the Linux-NTFS project. * * Copyright (c) 2001-2005 Anton Altaparmakov - * Copyright (c) 2002 Richard Russon + * Copyright (c) 2002-2005 Richard Russon * * This program/include file is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License as published @@ -214,8 +214,8 @@ static inline void __ntfs_rl_merge(runlist_element *dst, runlist_element *src) static inline runlist_element *ntfs_rl_append(runlist_element *dst, int dsize, runlist_element *src, int ssize, int loc) { - BOOL right; - int magic; + BOOL right; /* Right end of @src needs merging. */ + int marker; /* End of the inserted runs. */ BUG_ON(!dst); BUG_ON(!src); @@ -236,18 +236,19 @@ static inline runlist_element *ntfs_rl_append(runlist_element *dst, if (right) __ntfs_rl_merge(src + ssize - 1, dst + loc + 1); - magic = loc + ssize; + /* First run after the @src runs that have been inserted. */ + marker = loc + ssize + 1; /* Move the tail of @dst out of the way, then copy in @src. */ - ntfs_rl_mm(dst, magic + 1, loc + 1 + right, dsize - loc - 1 - right); + ntfs_rl_mm(dst, marker, loc + 1 + right, dsize - (loc + 1 + right)); ntfs_rl_mc(dst, loc + 1, src, 0, ssize); /* Adjust the size of the preceding hole. */ dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn; /* We may have changed the length of the file, so fix the end marker */ - if (dst[magic + 1].lcn == LCN_ENOENT) - dst[magic + 1].vcn = dst[magic].vcn + dst[magic].length; + if (dst[marker].lcn == LCN_ENOENT) + dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length; return dst; } @@ -279,18 +280,17 @@ static inline runlist_element *ntfs_rl_append(runlist_element *dst, static inline runlist_element *ntfs_rl_insert(runlist_element *dst, int dsize, runlist_element *src, int ssize, int loc) { - BOOL left = FALSE; - BOOL disc = FALSE; /* Discontinuity */ - BOOL hole = FALSE; /* Following a hole */ - int magic; + BOOL left = FALSE; /* Left end of @src needs merging. */ + BOOL disc = FALSE; /* Discontinuity between @dst and @src. */ + int marker; /* End of the inserted runs. */ BUG_ON(!dst); BUG_ON(!src); - /* disc => Discontinuity between the end of @dst and the start of @src. - * This means we might need to insert a hole. - * hole => @dst ends with a hole or an unmapped region which we can - * extend to match the discontinuity. */ + /* + * disc => Discontinuity between the end of @dst and the start of @src. + * This means we might need to insert a "not mapped" run. + */ if (loc == 0) disc = (src[0].vcn > 0); else { @@ -303,58 +303,49 @@ static inline runlist_element *ntfs_rl_insert(runlist_element *dst, merged_length += src->length; disc = (src[0].vcn > dst[loc - 1].vcn + merged_length); - if (disc) - hole = (dst[loc - 1].lcn == LCN_HOLE); } - - /* Space required: @dst size + @src size, less one if we merged, plus - * one if there was a discontinuity, less one for a trailing hole. */ - dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left + disc - hole); + /* + * Space required: @dst size + @src size, less one if we merged, plus + * one if there was a discontinuity. + */ + dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left + disc); if (IS_ERR(dst)) return dst; /* * We are guaranteed to succeed from here so can start modifying the * original runlist. */ - if (left) __ntfs_rl_merge(dst + loc - 1, src); - - magic = loc + ssize - left + disc - hole; + /* + * First run after the @src runs that have been inserted. + * Nominally, @marker equals @loc + @ssize, i.e. location + number of + * runs in @src. However, if @left, then the first run in @src has + * been merged with one in @dst. And if @disc, then @dst and @src do + * not meet and we need an extra run to fill the gap. + */ + marker = loc + ssize - left + disc; /* Move the tail of @dst out of the way, then copy in @src. */ - ntfs_rl_mm(dst, magic, loc, dsize - loc); - ntfs_rl_mc(dst, loc + disc - hole, src, left, ssize - left); + ntfs_rl_mm(dst, marker, loc, dsize - loc); + ntfs_rl_mc(dst, loc + disc, src, left, ssize - left); - /* Adjust the VCN of the last run ... */ - if (dst[magic].lcn <= LCN_HOLE) - dst[magic].vcn = dst[magic - 1].vcn + dst[magic - 1].length; + /* Adjust the VCN of the first run after the insertion... */ + dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length; /* ... and the length. */ - if (dst[magic].lcn == LCN_HOLE || dst[magic].lcn == LCN_RL_NOT_MAPPED) - dst[magic].length = dst[magic + 1].vcn - dst[magic].vcn; + if (dst[marker].lcn == LCN_HOLE || dst[marker].lcn == LCN_RL_NOT_MAPPED) + dst[marker].length = dst[marker + 1].vcn - dst[marker].vcn; - /* Writing beyond the end of the file and there's a discontinuity. */ + /* Writing beyond the end of the file and there is a discontinuity. */ if (disc) { - if (hole) - dst[loc - 1].length = dst[loc].vcn - dst[loc - 1].vcn; - else { - if (loc > 0) { - dst[loc].vcn = dst[loc - 1].vcn + - dst[loc - 1].length; - dst[loc].length = dst[loc + 1].vcn - - dst[loc].vcn; - } else { - dst[loc].vcn = 0; - dst[loc].length = dst[loc + 1].vcn; - } - dst[loc].lcn = LCN_RL_NOT_MAPPED; + if (loc > 0) { + dst[loc].vcn = dst[loc - 1].vcn + dst[loc - 1].length; + dst[loc].length = dst[loc + 1].vcn - dst[loc].vcn; + } else { + dst[loc].vcn = 0; + dst[loc].length = dst[loc + 1].vcn; } - - magic += hole; - - if (dst[magic].lcn == LCN_ENOENT) - dst[magic].vcn = dst[magic - 1].vcn + - dst[magic - 1].length; + dst[loc].lcn = LCN_RL_NOT_MAPPED; } return dst; } @@ -385,9 +376,10 @@ static inline runlist_element *ntfs_rl_insert(runlist_element *dst, static inline runlist_element *ntfs_rl_replace(runlist_element *dst, int dsize, runlist_element *src, int ssize, int loc) { - BOOL left = FALSE; - BOOL right; - int magic; + BOOL left = FALSE; /* Left end of @src needs merging. */ + BOOL right; /* Right end of @src needs merging. */ + int tail; /* Start of tail of @dst. */ + int marker; /* End of the inserted runs. */ BUG_ON(!dst); BUG_ON(!src); @@ -396,9 +388,10 @@ static inline runlist_element *ntfs_rl_replace(runlist_element *dst, right = ntfs_are_rl_mergeable(src + ssize - 1, dst + loc + 1); if (loc > 0) left = ntfs_are_rl_mergeable(dst + loc - 1, src); - - /* Allocate some space. We'll need less if the left, right, or both - * ends were merged. */ + /* + * Allocate some space. We will need less if the left, right, or both + * ends were merged. + */ dst = ntfs_rl_realloc(dst, dsize, dsize + ssize - left - right); if (IS_ERR(dst)) return dst; @@ -410,17 +403,28 @@ static inline runlist_element *ntfs_rl_replace(runlist_element *dst, __ntfs_rl_merge(src + ssize - 1, dst + loc + 1); if (left) __ntfs_rl_merge(dst + loc - 1, src); - - /* FIXME: What does this mean? (AIA) */ - magic = loc + ssize - left; + /* + * First run of @dst that needs to be moved out of the way to make + * space for the runs to be copied from @src, i.e. the first run of the + * tail of @dst. + */ + tail = loc + right + 1; + /* + * First run after the @src runs that have been inserted, i.e. where + * the tail of @dst needs to be moved to. + * Nominally, marker equals @loc + @ssize, i.e. location + number of + * runs in @src). However, if @left, then the first run in @src has + * been merged with one in @dst. + */ + marker = loc + ssize - left; /* Move the tail of @dst out of the way, then copy in @src. */ - ntfs_rl_mm(dst, magic, loc + right + 1, dsize - loc - right - 1); + ntfs_rl_mm(dst, marker, tail, dsize - tail); ntfs_rl_mc(dst, loc, src, left, ssize - left); - /* We may have changed the length of the file, so fix the end marker */ - if (dst[magic].lcn == LCN_ENOENT) - dst[magic].vcn = dst[magic - 1].vcn + dst[magic - 1].length; + /* We may have changed the length of the file, so fix the end marker. */ + if (dsize - tail > 0 && dst[marker].lcn == LCN_ENOENT) + dst[marker].vcn = dst[marker - 1].vcn + dst[marker - 1].length; return dst; } |