Hi,
static analysis with clang scan build has detected a potential issue
introduced by the following commit:
commit 7e9775a516ff6c1e73ee2b42ec563cafee38f42f
Author: Jaegeuk Kim <jaeg...@kernel.org>
Date: Fri Mar 10 11:12:35 2023 -0800
f2fs: factor out discard_cmd usage from general rb_tree use
The warning is as follows:
fs/f2fs/segment.c:1425:4: warning: Value stored to 'tdc' is never read
[deadcode.DeadStores]
The while loop in function __update_discard_tree_range is as follows (+
my annotations):
while (1) {
struct rb_node *node;
struct discard_cmd *tdc = NULL;
### tdc is set to NULL
if (prev_dc) {
di.lstart = prev_dc->di.lstart + prev_dc->di.len;
if (di.lstart < lstart)
di.lstart = lstart;
if (di.lstart >= end)
break;
if (!next_dc || next_dc->di.lstart > end)
di.len = end - di.lstart;
else
di.len = next_dc->di.lstart - di.lstart;
di.start = start + di.lstart - lstart;
}
if (!di.len)
goto next;
if (prev_dc && prev_dc->state == D_PREP &&
prev_dc->bdev == bdev &&
__is_discard_back_mergeable(&di, &prev_dc->di,
max_discard_blocks)) {
prev_dc->di.len += di.len;
dcc->undiscard_blks += di.len;
__relocate_discard_cmd(dcc, prev_dc);
di = prev_dc->di;
tdc = prev_dc;
### tdc is set to prev_dc, however, it is not not read any more with th
introduction of the "goto next"" statement introduced in the commit
mentioned earlier
goto next;
}
if (next_dc && next_dc->state == D_PREP &&
next_dc->bdev == bdev &&
__is_discard_front_mergeable(&di, &next_dc->di,
max_discard_blocks)) {
next_dc->di.lstart = di.lstart;
next_dc->di.len += di.len;
next_dc->di.start = di.start;
dcc->undiscard_blks += di.len;
__relocate_discard_cmd(dcc, next_dc);
### tdc is always NULL, there is no path to this code where tdc is ever
set to a non-NULL value.
if (tdc)
__remove_discard_cmd(sbi, tdc);
goto next;
}
__insert_discard_cmd(sbi, bdev, di.lstart, di.start,
di.len);
next:
prev_dc = next_dc;
if (!prev_dc)
break;
node = rb_next(&prev_dc->rb_node);
next_dc = rb_entry_safe(node, struct discard_cmd, rb_node);
}
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