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btrfs: avoid overhead when logging messages if fs state is clean

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If the fs state does not have any errors and is not in some special state
(like emergency shutdown or mounted with rescue options), then in
btrfs_state_to_string() we end up doing a memcpy() into the buffer and
then later just undo that work by setting the buffer's first element to
the NUL terminator, since fs_info->fs_error is 0 and there is no bit set
in fs_info->fs_state.

Improve on this by returning early if there's no error in the fs and the
fs state is clean, which is the expected scenario for a healthy fs that is
not mounted with special options like the rescue options.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Filipe Manana 2026-09-30 12:09:43 +01:00 committed by David Sterba
parent 719aee8396
commit 22bdddf40e
1 changed files with 9 additions and 9 deletions
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18
fs/btrfs/messages.c
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@ -33,27 +33,27 @@ static const char fs_state_chars[] = {
static void btrfs_state_to_string(const struct btrfs_fs_info *info, char *buf)
{
unsigned int bit;
bool states_printed = false;
unsigned long fs_state = READ_ONCE(info->fs_state);
char *curr = buf;
if (likely(BTRFS_FS_ERROR(info) == 0 && fs_state == 0)) {
*curr = 0;
return;
}
memcpy(curr, STATE_STRING_PREFACE, sizeof(STATE_STRING_PREFACE));
curr += sizeof(STATE_STRING_PREFACE) - 1;
if (unlikely(BTRFS_FS_ERROR(info))) {
if (BTRFS_FS_ERROR(info))
*curr++ = 'E';
states_printed = true;
}
for_each_set_bit(bit, &fs_state, BTRFS_FS_STATE_COUNT) {
if (fs_state_chars[bit]) {
if (fs_state_chars[bit])
*curr++ = fs_state_chars[bit];
states_printed = true;
}
}
/* If no states were printed, reset the buffer */
if (!states_printed)
/* If nothing printed, ensure we return an empty string. */
if (curr == (buf + sizeof(STATE_STRING_PREFACE) - 1))
curr = buf;
*curr = 0;